FWIW to the followers of this thread:
I have (had) an early 2008 15" MBP (1st Gen Multi-touch) that had the 8600 GT GPU in it. earlier this year I started having seemingly non graphics related issues. When closing firefox for example, the computer would just sit there processing the close for a few seconds, then the beach ball would appear for another 4-8 seconds, then the program would close. Took it to the genius bar and the diagnosed it as the GPU. They replaced the entire logic board and GPU and I had the same problem. After he second replacement and 4th trip to the Apple store, They are replacing my entire laptop with a new MBP. You don't have to have display issues for the GPU failure reak havoc.
I have (had) an early 2008 15" MBP (1st Gen Multi-touch) that had the 8600 GT GPU in it. earlier this year I started having seemingly non graphics related issues. When closing firefox for example, the computer would just sit there processing the close for a few seconds, then the beach ball would appear for another 4-8 seconds, then the program would close. Took it to the genius bar and the diagnosed it as the GPU. They replaced the entire logic board and GPU and I had the same problem. After he second replacement and 4th trip to the Apple store, They are replacing my entire laptop with a new MBP. You don't have to have display issues for the GPU failure reak havoc.