Many Avira users woke up to systems that either would not start up or could only be booted in secure mode. All this because of a glitch in Avira's ProActiv behaviour recognition module. The update called "service Pack 0" last Monday unexpectedly blocked the access to important system components. On Tuesday, Avira announced that it had solved the behavior recognition problem with an update.

Avira said that the patch can be installed by updating manually to solve the problem. What the company didn't say is that the update simply disables the ProActiv behavior recognition module – which is not even listed in the extended configuration dialog once the update has been installed.

The problem does not affect the free version of Avira, only the commercial version of its products. Plus it only affects users running the 32-bit version of Windows. The ProActiv module supports none of the 64-bit versions of Windows 7 and Vista; the free Avira Free Antivirus edition doesn't offer any behavior recognition by default.

It seems that Avira hasn't managed to tackle the ProActiv problem in the short term – completely disabling the module is, therefore, a plausible emergency measure. What's less plausible is that Avira has neglected to tell the users of Avira Antivirus Premium and Avira Internet Security that their protection is currently limited. Hopefully the developers will soon solve the problem and provide Avira customers with the comprehensive coverage that they currently pay for.