i joined duty at their base i had 35fps then i traveled to clear sky base and i noticed my memory usage was going up and my computer was running 10 to 8 fps by the time i made it to clear sky ??? i have 2g's sticks of memory ? ...but i dont get why going back to clear sky base eats up resources ? maybe you have to exit the game and reload the level hummm?
Its possible that there are memory leaks happening, though I haven't noticed any huge ones when I am playing (I monitor memory usage via RivaTuner)
Your fps will be low even the first time you enter the marsh due to so much open space and so much grass being rendered. Im getting an avg FPS of 30-40 with 3gigs of ram and an 8800GT anywhere in the game but in the marsh it drops dramatically, sometimes to 10-20 fps.
Do you remember what the FPS was when you first started playing in the marsh? Maybe when you return some things change like much more monsters but they shouldnt actually be rendered unless you see them and alife cant take THAT much ram usage. I think youre just experiencing the normal marsh lag but it maybe amplified a little by something.