Performance Drop in multiplayer

[Jarith]

Hi all, really enjoying the game. It's running great on my Gateway P-6831FX with everything turned up during the campaign, but when I get online and get into a match with a lot of units my framerate drops.

Good example of this is the second mission with the train trying to escape. Offline this runs smooth as glass. I played it last night with a friend in co-op and my framerate dropped significantly.

I have upgraded the CPU in my laptop with a Core 2 Duo 2.5GHz, and 4GB of RAM. It has a Nvidia 8800M and I am running Vista 32bit (came pre-installed).

Any ideas?