The purpose of this research study is to evaluate the effect of several daily doses of ketoconazole (a medication used to treat fungal infections like athlete's foot) on a single dose of GSK189075 (an experimental diabetes drug), and also to evaluate the safety and tolerability of GSK189075 in healthy volunteers. The study will see whether ketoconazole causes GSK189075 to stay in your bloodstream for a longer period of time. It will also examine whether GSK189075 causes any changes in the amount of glucose you have in your urine.