Cohorts of 3-6 patients in each subgroup (A1, A2, and A3) receive escalating doses of IDEC-Y2B8 until the maximum tolerated dose (MTD) is determined (subgroup A1 closed as of 10/8/04). The MTD is defined as the dose preceding that at which at least 2 of 3 or 2 of 6 patients experience dose-limiting toxicity (DLT).