Hi Kay:

Whenever you post here we need to know what version of Internet Explorer
you have and what version of Windows.

When posting the text of an error message we need to know what
application displayed the message and under what circumstances you see
the message.

Otherwise, you are asking us to make assumptions. And you know what
happens when you assume...

---
Leonard Grey
Errare humanum est

Do a thorough check for malware, following all of the steps at one of these
Web pages.
Help with malware:
All  MS-MVP Sites.
http://aumha.org/a/parasite.htm
http://aumha.org/a/quickfix.htm
http://www.elephantboycomputers.com/page2.html#Removing_Malware
http://mvps.org/winhelp2002/unwanted.htm
http://inetexplorer.mvps.org/darnit.html
http://www.mvps.org/sramesh2k/Malware_Defence.htm

Unexplained computer behavior may be caused by deceptive software.
http://support.microsoft.com/kb/827315

So How Did I Get Infected Anyway?
For quite a few people it's by installing Messenger Plus, whose ads for
malware don't identify the malware as such and try to convince you that you
owe it to the author.  See also:
http://www.wilderssecurity.com/showthread.php?t=27971
Don't ever do a "default" install of anything.  Always choose Custom and see
what else is being carried along.  Don't install any extras you're not sure
of.