ShineSyndrome

I am using a wired netgear 4 way router which runs fine when attached to my laptop. However when it is connected to my PC the internet traffic slows to practically a stand still after 5 minutes. Programs that use the internet (Steam, messenger etc.) time out and refuse to connect and certain websites (such as facebook) won't load up. My anti-virus shows that the system is clean, the other problem with my system is that it sometimes takes a very long time to shut down. My ISP is Tiscali and I'm using a 1meg unlimited connection. For the virus scans I have used AVG and Ad-aware. Any ideas?