Why are you guys so set on Spyware and Antivirus programs? Its a problem with Microsoft's services. It happens with IE and Firfox. Anyone notice that if you leave it alone and don't reboot. Sometimes It will start working again.
I have a Dell 1521 and this has been happening right out of the box. With nothing installed but what came with it. I use both, Wireless and Hardwire. Believe it or not but this problem happens more when Im hard wired then wireless.

And this is Vista Home Prem.