A virus definition update for AVG 2011 Free edition seems to be causing problems for Windows 7 64-bit users.
[UPDATE: I'm hearing from some users of the non-free version of AVG 2011 who say that they are also affected.]
The update was released today at 12:53 AM CET and causes a problem when the system is rebooted, where the following error is displayed
STOP: c0000135 The program can't start because %hs is missing from your computer. Try reinstalling the program to fix this problem.
If you're affected, three possible solutions are presented here. Also listed is a fix for those who have installed the update but not yet rebooted their systems.