IF you are running your BIOS Clock at UTC,
AND you are running Windows 7 in your local timezone
AND your local timezone is WEST of UTC,
AND ( Daylight Savings (Ends OR Finishes)
OR the year changes )
THEN your machine will lock up
AND will not boot
AND system restore will not work
AND recovery console will not work
UNTIL midnight UTC is reached (because internally some value goes negative (which is very largely positive for unsigned values)).
It locks so hard, even trying to boot to safe mode, that the caps lock light won't even come on.
If you can boot up in a timezone EAST of UTC it comes up OK.