"ULwindowURL" How can i stop this?

I keep getting this pop up every so often. Ive tried to remove it Via Norton Anti Virus but to no avail. How can i remove it?

http://img506.imageshack.us/img506/8251/46565656565655665657cu.jpg

anyone? Its becoming very annoying

How do you get all these viruses?

Seriously, what do you do on your computer?

All i do is surf the internet, do some CGI, download Movies, Tv shows and music. The bad thing is, my virus scanners arent picking up anything

Has getting a new virus scanner ever occured to you?

tried, some i tried to get turned out to be virsues them selves (thankfuly picked up by norton)

http://www.grisoft.com/doc/289/lng/us/tpl/tpl01

This is AVG antivirus software. It's free and it could get you out of trouble. It's a pretty good antivirus program. It worked for me when I had problems with norton. I've since changed to McAfee.