McAfee’s 5958 virus definition update crippled workstations today, causing “false positive identification of the critical Windows system file svchost.exe; machines running Windows XP Service Pack 3 using the 5958 definitions will delete the file, causing many key Windows services to fail to start.” Here’s what they recommend you do until a permanent fix is offered:
Boot the system into safe mode. Drop the attached extra.dat in c:/program files/common files/mcafee/engine. Reboot into normal mode. Rebooting into Windows normal mode type “shutdown /a” in the run line this aborts the automatic shutdown.