I have a Late 2006 MacBook Pro. I installed Windows 7 32-bit, then I installed Boot Camp 2.0 from the Leopard DVD (as the Boot Camp 2.1 update wouldn't run), rebooted, and then I was planning to install the 2.1 update.
After rebooting, the desktop loads for a few seconds and then the whole computer hangs. This only happened after installing Boot Camp 2.0. I have tried booting into Safe Mode and disabling a heap of stuff (Radeon X1600 drivers, Firewire, Ethernet, Bluetooth, iSight, etc.) but it still won't boot.
I narrowed down the cause of my rebooting problem to the C:\Program Files\Boot Camp\KbgMgr.exe startup entry. I am not sure why having it in Startup causes a complete system hang, while starting it separately from startup just causes it to crash ("has caused a problem and has been closed").