Latency spikes in random games.

For some peculiar reason I am getting lag spikes in *some* multiplayer matches in demigod. They occur once every two or three seconds, enough to make a game unplayable and embarassing me in the process. I have to be the one to ruin a game. I noticed it is more pronounced in 4v4 games in leviathan. When I connect to the game lobby it shows others having a ping of 100-150. Others report my ping is around that as well. However once the game starts other players repot my ping skyrocketing to 350 or higher every few seconds. This occured in US-based games, east cost, west coast, doesnt matter. It never crashes but again it ruins that match and pisses off alot players.

My ISP is earthlink, and I am using a DSL connection. I have port forwarding enabled, a static IP etc. I have turned windows firewall off completely as well. Is there anything else I can do? I am not downloading or even viewing other websites while the game is playing. Could any of windows services be interfering? I saw in one post a mentioning of packet sniffing, causing lag spikes. I am willing to try about anything to fix this problem.