AVG, the very popular free anti virus scanner, erroneously detects a critical Windows file as a virus and warns users to remove it, crippling the system.
An update for the AVG virus scanner released yesterday contained an incorrect virus signature, which led it to think user32.dll contained the Trojan Horses PSW.Banker4.APSA or Generic9TBN. AVG then recommended deleting this file; this causes the affected systems to either stop booting or go into a continuous reboot cycle. So far, the problem only appears to affect Windows XP, but there is no guarantee that other versions of Windows don’t have the same issue.
Both AVG 7.5 and AVG 8.0 were affected by the erroneous definition file. The file has since been update to remove the error. AVG has posted FAQs as well as a fix for affected users on their support site.
For affected users, you can either reinstall Windows or do a repair install with a Windows disk. A third option is to use a boot disc, such as the Ultimate Boot CD (ISO) and then grab the files you need from the "C:\Windows\System32\dllcache" directory.