Fortunate for Windows Vista & Windows 7 folks, this only affected Windows XP PCs:
Buggy McAfee update slams Windows XP PCs | Security - CNET News
Early reports attributed the widespread problems to a routine McAfee update that caused computers with Microsoft's Service Pack 3 installed to incorrectly identify a legitimate operating system component as containing a virus.
A McAfee representative confirmed the problem to CNET, and said the buggy update code had been removed from the company's servers and that a fixed version would be made available shortly.
"McAfee is aware that a number of customers have incurred a false-positive error due to incorrect malware alerts on Wednesday, April 21. The problem occurs with the 5958 virus definition file (DAT) that was released on April 21" at 6 a.m. PT, the company said in a statement.
ICS reported that it was a false positive which identifies a regular Windows binary, "svchost.exe", as "W32/Wecorl.a", a virus.
Recovery information at ICS: McAfee DAT 5958 Update Issues