Some users of AVG were left with unusable Windows systems after the popular AVG security scanner software slapped a Trojan warning on a core Windows component.

AVG tagged user32.dll as a banking Trojan following a signature update issued on Sunday, advising users to delete the "harmful file". Users following this advice would be left with systems that either failed to boot or went into a continuous reboot cycle, according to dispatches from those hit by the glitch.

Users of both AVG 7.5 and 8 (free and full fat editions) were hit by the snafu. AVG has admitted the problem and responded by posting advice on how to recover affected systems (via its support forum item 1574 - here). The company has also updated its virus definition files to purge the false alarm detection from its virus signature database.