bill - 6:30 am on Dec 3, 2010 (gmt 0)
AVG Free Update Bricks 64-Bit Windows 7 PCs [pcworld.com]
If you haven't already downloaded the latest mandatory AVG 2011 Free software update, it may be best not to if you want your computer to turn on again. The December 1 update is causing 64-bit PCs running Windows 7 to totally breakdown.
The problem appears to lie in the 271.1.1/3292 (432/3292) database update, which requires PCs that run the update to restart. Affected PCs will throw up a c0000135 error upon restarting, and fail to boot.