Need help with my new upgrade.

so i ended up getting rid of my 7950gx2 and getting a 2900pro and a water cooling system for the cpu. i got everything set up, installed the 7.10 drivers for my video card, and did a fresh install of windows. after getting all my temp reading to make sure nothing is overheating and that everything is on the safe side, i started trying to benchmark and play some video games. here come the problems:

-sometimes i notice some jerks in games with the new card.
-when i over clock the card, i get no performance benefit at all.
-3D and PC mark stop responding when they are collecting system information

here's the specs:
A8N32-SLI Deluxe
AMD 4800+ w/o IHS overclocked to 2.7GHz
2GB OCZ Golden Gamer DDR 450 at 2.5-3-3-5 1T
Sapphire 2900Pro
520W Corsair Power Supply and 250W Thermaltake VGA Power Supply
74GB Raptor Main Drive

the average fps of some of the games i play:
TimeShift: 52FPS
Need For Speed Carbon: 75PFS
Lost Planet (DX9): 30FPS
GRAW 2: 45-50FPS
Clive Barker's Jericho: 50-55FPS

overall, decent performance, but like i said, even if i overclock, i get no performance boost at all. and it's quite annoying that all the benchmarks i run stop responding.

Could it be the cpu holding me back in gaming, or maybe the nf4 chipset isn't playing too nice with the video card?

any help is appreciated.

thanks . I'm just frustrated with the futuremark programs not working and the lack of performance benefit when i overclock