Kohenkatz writes "A McAfee Update today (DAT 5958) incorrectly identifies svchost.exe, a critical Windows executable, as a virus and tries to remove it, causing endless reboot loops."
Reader jswackh adds this terse description: "So far the fixes are sneakernet only. An IT person will have to touch all affected PCs. Reports say that it quarantines SVCHOST. [Affected computers] have no network access, and missing are taskbar/icons/etc. Basically non-functioning. Windows 7 seems to be unaffected."
Updated 20100421 20:08 GMT by timothy:
An anonymous reader points out this easy-to-follow fix
for the McAfee flub.