Windows Update downloaded the latest security update (KB925902), but after restart I got the folllowing error message:
RTHDCPL.EXE – Illegal System DLL Relocation. The system DLL user32.dll was relocated in memory. The application will not run properly. The relocation occurred because the DLL…
Alrighty!!! A patch gone wrong, apparently. On today I guess, the same day they released that security patch, Microsoft issued a hotfix (KB 935448). Notice that you may get errors while getting to the actual download: it appears that this fix is quite popular. If you run a RealTek card, you probably ran into the same issue. Particularly, if you own a Toshiba laptop.
Oh: and talking about patches, you may also consider updating your WordPress (see also here for more details).
04/04/07: Slashdot discusion.
04/11/07: A weeks later, the issue brought up over at the BBC.