Users of the BitDefender anti-virus software started flooding the company's support forums Saturday, apparently after a faulty anti-virus update caused 64-bit Windows machines to stop working.

The company acknowledged the issue in a note explaining the problem, posted Saturday. "Due to a recent update it is possible that BitDefender detects several Windows and BitDefender files as infected with Trojan.FakeAlert.5," the company said.

The acknowledgement came after BitDefender users had logged hundreds of posts on the topic. Some complained of being unable to reboot their systems.

"EVERY file that is trying to run is getting quarantined," one user, identified as lhmathys, reported. "Windows Explorer and even Bitdefender update itself is being quarantined. Someone really screwed this one up."

"We are in a really terrible position now," wrote another user, identified as ufitec. "We have 150 business clients and most of the pcs [on] which BitDefender thinks everything is virus does not boot any more!!!!"

Full story: InfoWorld