ARM III: Patients receive gemcitabine hydrochloride IV over 30 minutes on day 8 and tanespimycin IV over 1 hour on days 1 and 9 of course one. Beginning with course two (and for all subsequent courses), all patients receive gemcitabine hydrochloride IV over 30 minutes on days 1 and 8 and tanespimycin IV over 1 hour on days 2 and 9.