In a demonstration of how serious it can be when antivirus software goes awry, today an update from Avira for its antivirus software is wreaking havoc across the globe as it blocks some of Windows' most important processes, such as explorer.exe, rundll32.exe and dllhost.exe. The program is falsely detecting these as viruses and killing them, which effectively cripples the OS. But that's not all - other major programs (Opera, Google Talk, even Microsoft Office) are being blocked.
This only affects the paid editions of the software, including the business editions. Read more here: