A recent VirusScan update from McAfee caused mayhem for some IT administrators over the weekend, after it falsely reported that a range of critical system files were infected with a Trojan.

The problem became apparent when users began posting to the company's forums, complaining of false positives and even some cases of the dreaded blue screen of death.

The issue seems to affect only those users running an outdated version of the VirusScan engine, but some running the latest version also reported false positives, although not with critical system files.

McAfee has acknowledged a problem, and has released another update which corrects it. However, it appears that machines affected by the glitch will have to be repaired manually, as the quarantined files cannot easily be returned to their original locations.

"Last Friday, McAfee was made aware of some incorrect identification when using no longer supported versions of the software," explained a McAfee spokesman.

"Customers reporting this issue have been confirmed to be running VirusScan Enterprise 7.1 or 8.0i specifically with the 5100 scanning engine that has not been supported for 18 months.

"Customers running 5200 or a newer scanning engine version have not been impacted. Current versions are VSE8.7 and scanning engine 5301. The incorrect identification was resolved in the daily release on Friday July 3rd."

The company has created an entry in its KnowledgeBase detailing the issue and offering potential fixes for those affected.