Crysis help

Hello, I have (what i thought was) a pretty powerful set-up but i can only seem to get a good 20 fps in crysis and as low as 5 fps and temporary freezes when in action. When i first started playing the game i got a solid 60 fps just wandering around and taking out the first few guys. but now into the 3rd and 4th level i suffer just to squeeze out a playable game. I have installed all latest drivers, patch 1.2, even tried overclocking GPU's and CPU. Any help would be great.

1600X1200 no AA all specs ONLY MEDIUM

Asus M2n32-sli Deluxe
AMD 6400+ black edition (overclocked to 3.4)
patriot 6400 2 GB RAM
2X bfg 8800 GT OC in SLI
80 hitachi laptop HD (so quiet, i love it)
500 Watt power supply

I'll second that, your PSU is not enough if you overclock + SLI. You need at least a good PSU at 600W if you want to do this.

This might sound dumb but just in case you're new to PSUs. A good PSU at 600W is much better than a cheap PSU 900W. Though, they are usually a little more expensive.

Nota: Never get a cheap PSU if your a gamer...because it'll loose all its juce as soon as it heats a little.

yer my 480w PSU can hardly handle my single OC 8800gt and OC CPU. Im looking at 520 corsair HX, it isnt much more, but the quality is meant to be very good.