Patients with a history of any one or more of the following thromboembolic events within the past 6 months prior to study enrollment are NOT eligible for participation: \r\n* Pulmonary embolism\r\n* Untreated deep venous thrombosis (DVT)\r\n** Subjects with recent DVT who have been therapeutically coagulated for at least 6 weeks ARE eligible Cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months\r\n* Note: subjects with recent DVT who have been therapeutically coagulated for at least 6 weeks are eligible History of a major thromboembolic event =< 6 months prior to randomization, including cerebrovascular accident, transient ischemic attack (TIA), myocardial infarction, symptomatic pulmonary embolism (PE) or untreated deep venous thrombosis (DVT), or coronary artery bypass graft surgery; NOTE: Subjects with recent DVT or asymptomatic PE who have been treated with therapeutic anticoagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism, or untreated deep venous thrombosis (DVT) within the past 6 months Any of the following conditions =< 6 months prior to registration:\r\n* Cerebrovascular accident (CVA) or transient ischemic attack (TIA)\r\n* Serious or unstable cardiac arrhythmia\r\n* Admission for unstable angina or myocardial infarction\r\n* Cardiac angioplasty or stenting\r\n* Coronary artery bypass graft surgery\r\n* Pulmonary embolism, untreated deep venous thrombosis (DVT) or DVT which has been treated with therapeutic anticoagulation =< 30 days\r\n* Arterial thrombosis\r\n* Symptomatic peripheral vascular disease Cerebrovascular accident at any time in the past, transient ischemic attack, deep venous thrombosis or pulmonary embolism in the past 6 months History of cerebrovascular accident including transient ischemic attack, pulmonary embolism (including asymptomatic or previously treated pulmonary embolism [PE]), or untreated deep venous thrombosis within the past 6 months; patients with recent deep vein thrombosis (DVT) who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; note: subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), myocardial infarction, pulmonary embolism or untreated deep venous thrombosis (DVT), coronary artery bypass graft surgery within 6 months prior to registration; Note: subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible Patients with a history of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or insufficiently treated deep venous thrombosis (DVT) within the past 3 months; Note: Participants with recent DVT who have been treated with therapeutic anti-coagulants for at least 6 weeks are eligible, with the exception of participants being treated with warfarin, which is prohibited on this study; other oral anti-coagulants may be allowed after discussion with overall principle investigator (PI), but short half-life low molecular weight heparins are strongly preferred History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; Note: patients with recent DVT who have been treated with therapeutic anticoagulation agents for at least 6 weeks are eligible as long as their INR is stable and within inclusion criteria above History of cerebrovascular accident including transient ischemic attack, pulmonary embolism (PE) (including asymptomatic or previously treated PE), or untreated deep venous thrombosis within the past 6 months; patients with deep venous thrombosis (DVT) who are being treated with therapeutic anti-coagulating agents are eligible Angina, MI, symptomatic congestive heart failure, cerebrovascular accident, transient ischemic attack, arterial embolism, pulmonary embolism, PTCA or CABG within the past 6 months. Deep venous thrombosis within 6 months, unless the patient is anti-coagulated without the use of warfarin for at least 2 weeks. In this situation, low molecular weight heparin is preferred. Angina, MI, symptomatic congestive heart failure, cerebrovascular accident, transient ischemic attack, arterial embolism, pulmonary embolism, PTCA or CABG within the past 6 months. Deep venous thrombosis within 6 months unless the patient is anticoagulated without the use of warfarin for at least 2 weeks. In this situation, low molecular weight heparin is preferred. History of stroke, deep venous thrombosis (DVT), or transient ischemic attack (TIA) Previous history of cerebrovascular accident (CVA), transient ischemic attack (TIA), angina pectoris, acute myocardial infarction (MI) or history of recent re-perfusion procedures (e.g. percutaneous transluminal coronary angioplasty [PTCA]), pulmonary embolus or untreated deep vein thrombosis (DVT) within 6 months from day 1 of study drug; NOTE: subjects with recent DVT who have been therapeutically anti-coagulated for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months. History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; Note: subjects with recent DVT who have been treated with therapeutic anticoagulating agents for at least 6 weeks prior to study treatment are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months Patient must not have a history of cerebrovascular accident including transient ischemic attack within the past 6 months; patients with recent deep venous thrombosis or pulmonary embolism who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible as long as INR is stable History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within 6 months of registration; note: subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks prior to registration and are fully anti-coagulated are eligible History of pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; Note: Patients with recent DVT who have been treated with therapeutic anticoagulation including Coumadin or any low molecular weight heparin for at least 6 weeks are eligible History of cerebrovascular accident (CVA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; Note: subjects with recent DVT who have been treated with therapeutic anti-coagulant agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; Note: subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack, untreated deep venous thrombosis (DVT) or pulmonary embolism within the past 6 months; patients with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; note: subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible but must be monitored regularly for changes in relevant coagulation parameters as clinically indicated as well as any clinical bleeding episodes History of cerebrovascular accident, pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible EXPANSION COHORT ONLY: History of cerebrovascular accident, pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism, or untreated deep venous thrombosis (DVT) within the past 6 months; subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months. History of cerebrovascular accident including transient ischemic attack, pulmonary embolism, or untreated deep venous thrombosis within the past 6 months. History of cerebrovascular accident, pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible History of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months; note: subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible Deep venous thrombosis (DVT) diagnosed within 12 months of study enrollment or history or untreated lower extremity DVT, bone metastases, currently active skin infection, or lymphedema currently involving the treatment field Patient must not have history of cerebrovascular accident including transient ischemic attack (TIA), pulmonary embolism or untreated deep venous thrombosis (DVT) within the past 6 months\r\n* Note: subjects with recent DVT who have been treated with therapeutic anti-coagulating agents for at least 6 weeks are eligible