I just had that happen too, I have two virus checkers (Symantec and Trend
Micro) that couldn't locate the worm. these are daily updated patterns too.
Spybot S&D and Trojan remover couldn't locate it either. After a day of
searching I found a reference to a file called "msrun32.exe" this is the
virus file. To remove it boot in safe mode, using explorer (My Computer),
navigate to your %windows\system32 directory and find the bad file. The
file is hidden so you must configure explorer to allow you to see hidden
files. You cannot delete it unless you are logged in as admin, even then
there is a trick. Right click on it and set the permissions to full then
you can delete it or just change the extension and send it off to one of the
virus companies.
Next you must remove any entries in your MSconfig and do a registry search
for it
Oh I forgot before you reboot to safe mode turn off system restore on all
drives. Once you get this worm, you can turn system restore back on.
Cheers