I had the exact same issue as you, Arctucas, although I uninstalled the Spybot beta from Safe mode after two STOP 0x50 errors and everything appears back to normal. The crashes occurred within two minutes of booting into Windows (7 SP1 64-bit) for me. I've never had any problems with the older v1.6.2 so I'll stick with that I think until the RC or final build.
Blue screen crashes are a very, very rare occurence for me and usually a result of software conflicts (e.g. HD 5870 CFX + EVEREST) or dodgy drivers/software; I can the number I've had over the past three years on one hand and still have fingers spare!!!