"STOP: c0000135 The program can’t start because %hs is missing from your computer. Try reinstalling the program to fix this problem."
AVG released a virus signature database update (version 271.1.1/3292 (432/3292) ) on December 2, 2010 that prevented some 64-bit Windows 7 computers running the Free Edition of AVG from completely booting – forcing the systems into a reboot loop.
They’ve put instructions on their forum on how to solve the problem.
Notice that there are several posts – don’t just read the first one…
They’ve also posted a FAQ and information on their support page.