The purpose of this study is to find a dose of SB-743921 in adult patients with solid tumors or lymphoma who have progressed on standard therapy or who have relapsed. SB-743921 is dosed by 1-hour intravenous infusion every 3 weeks. A patient may continue to receive treatment as long as they are benefiting from the treatment. Blood samples will be taken at specific times to measure the amount of the drug in your body at specific times after the drug is given. Blood samples will also be taken for lab tests such as complete blood counts and clinical chemistries. Physical exams will be performed before each treatment with SB-743921. During the treatment phase, the patients will undergo regular assessments for safety and clinical response.