Try deleting your spyware every time before you play. Use Spyware - Search and Destroy (occasionally) to get rid of marketing programs and Ad-Aware (often) to get rid of the rest. www.download.com hosts genuine copies. Make sure you check for updated definitions every time before running.

Also make sure that you don't have Kazaa, Limewire etc. running when you play.

Okay I am having problems now as well...

I just swapped my cheap piece of rubbish wireless/RJ45 router for a D-Link one. Now my laptop stays connected to the net, but I cannot even complete a game of 9-ball. Back to the shop :)