The primary objective of this phase I study is to determine the safety, tolerability and optimal tolerated regimen of GW572016 when combined with gemcitabine and with the combination of gemcitabine and oxaliplatin. Three to six patients will be treated at each dose level to assess toxicity. To better assess the safety at the final dose level in both Stage I and Stage II, the number of patients in the cohort at the Maximum Tolerated Dose for both Stages will be expanded to 10. Therefore approximately 34-37 patients will be treated on this study.