If the problem was caused by a recent Windows Update, uninstalling it should
fix it. Go to Windows Update and click on the Update History link in the
left-hand pane to see updates recently installed. Note especially the KB
number associated with each update (e.g., KB903235 for MS05-037) then go to
Add/Remove Programs, find the update (make sure Show Updates is checked at
top of window), uninstall it and reboot.
The problem may have been caused by Malicious Software which the Malicious
Software Removal tool, er..., removed. If so, the behavior's being caused
by leftover files the tool didn't remove. (The tool's a work in progress
and, like your anti-virus application, can never be truly realtime,
up-to-date when it scans.) See next paragraph.
To be honest, too, your problem sounds like a hijackware infection. You
should at least rule it out.
Checking for/Help with Hijackware
http://aumha.org/a/parasite.htm
http://aumha.org/a/quickfix.htm
http://aumha.net/viewtopic.php?t=5878
http://mvps.org/winhelp2002/unwanted.htm
http://inetexplorer.mvps.org/data/prevention.htm
http://inetexplorer.mvps.org/archive/tshoot.html
http://www.mvps.org/sramesh2k/Malware_Defence.htm
http://defendingyourmachine.blogspot.com/
When all else fails, HijackThis v1.99.1
(
http://aumha.net/downloads/hijackthis.zip) is the preferred tool to use.
It will help you to both identify and remove any hijackware/spyware. **Post
your log to
http://forums.spywareinfo.com/,
http://castlecops.com/forum67.html or
http://aumha.net/viewforum.php?f=30
for expert analysis, not here.**
Hang in there and let us know how you make out.