It's bad news when your anti-virus package breaks games, and worse when it kills Windows, but when it begins attacking other anti-virus products people start asking questions.

That's the unenviable situation Avira has found itself in after its popular anti-virus package detected a beta release of competing software BitDefender 2011 as a Trojan - leaving any users attempting to try out the beta without un-installing their existing anti-virus fighting a false-positive warning.

First reported by a Romanian blog and then picked up - and translated - by The Register, a fix has now been put in place to prevent the false positive, but the experience will have left many with a sour taste in their mouths and Avira with a tattered reputation.

Avira's Sorin Mustaca confirmed that his company's anti-virus "mistakenly reported that the BitDefender 2011 product, that hasn't been publicly released yet, was a Trojan,[i]" and blamed the issue on "[i]some components in the installer [being] modified so that the digital certificates became invalid" for the false positive.

BitDefender's Vitor Souza was quick to point out that the false positive was "an issue with [Avira's] detection, and not a problem with BitDefender."

Although only likely to have affected a small number of users - it's rare, after all, to install two competing anti-virus packages on the same system - it's an embarrassment for Avira and one which could have left it facing BitDefender in the courtroom if it hadn't resolved it as quickly as it did.

Are you surprised to see that anti-virus companies still aren't able to resolve the issue of false positives, or will these problems continue to occur until a detection system that isn't signature-based is perfected? Share your thoughts over in the forums.