Last night I ran a software update on my iMac 27'', 2.8 GHz, i7 QuadCore with 8 Gb of DDR3 RAM, and ever since I haven't been able to boot up in Windows 7 Ultimate 64-bit version. Windows was installed last year and I have never had any problems with this until last night. Anyone else with this problem? I've tried reinstalling Mac OS X 10.6.2, leaving the bootcamp partition intact, but no luck. When I restart and keep ALT down to choose which system to start I see both Windows and MAc, but selecting Windows gives me a blank white screen and nothing happens.