A very bad service pack 0 has caused Avira Version 2012 (pay for versions with ProActiv) to cause .exe files to be quarantined, sometimes bricking a Windows PC:

http://www.computerworld.com/s/article/9227182/Avira_antivirus_upgrade_wreaks_catastrophic_havoc_on_Windows_PCs?source=CTWNLE_nlt_pm_2012-05-15

OOPS!

They are the number-one most wanted target by hackers and virus authors because they are free, and,at least outside the US, have a huge installed base. The paid version added some bells and whistles, and now this.

Microsoft Security Essentials works for me, after a couple of bad Avira updates a year or so ago.

bricking a Windows PC

I wish people stopped to use this term for pretty much anything.

"Bricking" means breaking an electronic device beyond repair, making it pretty much as useful as a "brick".

I doubt this Avira bug does more than just requiring you to reinstall windows.

edit: And I agree with Sateev: Microsoft Security Essentials is the best you can get currently (and it's free, but you need to have a genuine version of windows).

Semantics.

I found this reference that sums it up as Bricking

Nothing to rule out a major sw install to recover, that I can see.

ZoneAlarm did the same to its customers a few years back and that was a paid version too...........