Windows 7 - Why would my mouse's (sp?) right click and rollerball function quit?

Mysteriously, I have lost some functionality in my mouse - specifically the roller/clicker no longer lets me scroll, or any other funtion assigned to it.

I very recently had Norton remove about 10 viruses - got infected by all ten at cnet.com, by the way - I had always assumed that site to be mal/spy ware free.

Anyway, I had to reinstall using an image I had taken recently in a full backup. I then ran Norton, CounterSpy (who tell me they are going to stop supporting that next fall, and are trying to get everyone to jump ship over to Vipre. (the version w/o a firewall of course).

Other than that one thing, my sys seems bug less, but sometimes tiny things like this are the very tip of a huge iceburg you are about to steam into at full speed.
I will welcome any suggestions! Thank you all!
Joe

Have you tried another mouse to eliminate a hardware issue with this one? I'm saying this because the previous mouse I had before the one I'm now using developed a fault whereby the left mouse button was no longer being recognised.