Somethings very wrong with your box. If you figure out what, tell me.
I guess we'll never know, but FYI, m0mchil's GPU miner works like a charm for me with its default settings. I am getting 155 Mhash/sec with default settings, and 177 Mhash/sec with some tuning -- without any crashing. There must be some flaw with your implementation. If you figure out what, tell me.