<qa>  What is the goal of this clinical research study?The goal of this clinical research study is to find the highest safe dose of the new drug ZARNESTRA R115777 and temozolomide that can be given to patients with brain tumors glioblastoma multiforme, GBM. The second goal is to learn if these drugs given in combination can shrink or slow the growth of brain tumors. The safety of this treatment will also be studied. 