AVG, one of the leading suppliers of anti-virus software, released an update yesterday that caused more harm then good the outcry started. The signature update, dated November 9, allowed the program to think that user32.dll was actually a trojan and advised you to delete it but it doesn't stop there, if you do delete it and you restart your computer it will put your computer on a continuous reboot loop.
Both AVG 7.5 and 8.0 were affected by this signature update problem and at the time of writing this article XP seemed the most affected operating system, if you have had the reboot problem and want to know how you can get around it Security and the Net Blog posted this to help the users "People that have removed the user32.dll can either boot from their original Windows CD and choose the repair option, or use another CD to boot from and restore the file from C:\Windows\System32\dllcache".
AVG has responded to these problems on their forum thanking the users for their patience and help in this matter, "Unfortunately, the previous virus database might have detected the mentioned virus on legitimate files. We can confirm that it was a false alarm. We have immediately released a new virus update (270.9.0/1778) that removes the false positive detection on this file. Please update your AVG and check your files again".