It could possibly be a bad router. But thats just a speculation.
I had an Airlink101 AR625W Wireless draft N router, and I was getting like, 400 ping on a server I used to get 7 ping on. Plus, the router itself was trash, it kept disconnecting all of my computers and restarting itself all the time.
So I just did the deed, and bought a D-link DGL-4300 G gaming router. That basically fixed the problem I had with the ping and the random disconnects. So now instead of having 400+ ping on CS-S and HL2 DM servers, i went back down to 10 +/- ping, and thats while using three others computers at the same time.
Hope this helped. If you have anymore questions, please post em
Borgslayer