Yeah, I know. Posting 2 months later...
Just wanted to say for posterity that I have GoBack 3.11 running on both my Win2K box and my WinXP box, and it was installed and running for SP1, SP2, and SP3 installs on Win2K and for the SP1 install on WinXP. I had no such issue.
Then again, I don\'t own a Thinkpad.
I would bet real money that the original user (thread poster) had either a corrupted or incorrect Hard Drive Filter driver loading on the system. When he/she installed SP3, the act left Windows trying to load a driver to filter Hard Drive access through that was either missing or broken. This is a guaranteed way to get Windows 2K or XP to die on boot.
Best guess: IBM had RapidResume or RapidRecovery or something like it (system restore, like GoBack) on the system and it naturally had to have filter-level access to the Hard Drive. Installing SP3 either removed the reference without changing the data structure on the drive to allow standard (non-filtered) access or removed the driver without removing its reference.