Problems playing CSS with a router

[Mac2]

I have just bought a Linksys WRT54GS router to share my broadband with my flatmate, although he's not connected yet.

The router is working, as web browsing etc is fine, but when I try and play CSS the server browser is sluggish and doesn't show up as many servers as normal. Googling suggests it might be something to do with port forwarding but can anyone else help?

 

[mosehn]

i have the same router and i cant even connect to servers but i can get a server list up , it used to work really good , now i have this problem and have to disconnect the router when i am using steam.