Every time I reboot from Boot Camp into OS X, the bootloader gets to the login screen, and then after I've entered my username and password, the screen will just go grey. I have to force a restart with the power button, and then when I reboot, it proceeds normally.
Specifics: Windows 7 Professional 32-bit in Boot Camp, and OS X 10.7.1. The same issue happened with 10.7.0. This is on a late-2008 MacBook Pro 15".