BleepingComputer.com: games stuttering even though running at 60fps

I'm running a q6600 at stock speeds (2.4ghz) with an ati 5850 (just replaced an 8800gtx) and 4gb ram on win7 64. I'm running the latest ati drivers and trying to run these games 1920x1200

I noticed that in a handful of games like Oblivion, Alien Swarm (steam), and Booster Trooper (steam) are stuttering every few seconds even though fraps says i'm getting a stable 60fps with vsync on.

then other games like bioshock 2, counter strike source, and starcraft II don't have any issues.

I tried OC'ing to 3.0ghz with the same results. I'm not sure if it's a cpu bottleneck and I should upgrade to a newer processor. I didn't see any kind of cpu spiking though that might be causing the problem.

Anybody have any tips for troubleshooting what could be the cause? I have tried different resolutions on some of the games and it helped but oblivion I get skipping no matter what, even running at 800x600 getting over 150fps while inside a building.

I just don't understand why FRAPS is saying a steady 60fps in these games and yet they are still stuttering.