I’m running the most up-to-date steam version of the game with all DLC. It’s a recent re-install, completely vanilla with no mods of any sort running right now. Brand new game, so no save issues. I’ve previously run the game on this same system at medium to high settings with no issues, with a fair number of mods installed.

The problem is that randomly but reliably (anywhere from ten or fifteen minutes playing to right after loading the game) the framerate starts, well pulsing, for lack of a better word. I’ve used fraps to check it and it doesn’t seem to actually be affecting the registered FPS, but there’s noticeable slowdown for just a brief moment about every two seconds, it might be too brief for FRAPS to catch, I don’t know. It’s most obvious with movement, because it gives the appearance of things slowing down and speeding up, but it doesn’t actually stutter and stop entirely. I’ve tried everything I can think of at this point to stop it, increasing allocated memory, turned vsync on and off, messed with all of the normal settings, nothing reliably gets rid of it.

My system is an ASUS G60vx laptop running Windows 7 Home Premium x64 with SP 1.
CPU: Intel Core 2 Duo 2.13 GHz
RAM: 4 GM
GPU: nVidia GTX 260m with 1GB memory and the most recent drivers (GeForce 310.90)

I’m about ready to stab something, any help is greatly appreciated.

Sounds like something running in the background. Check the Windows' log files to see if anything was running.

Nothing but background processes. I've even tried running the bloody thing windowed so I could monitor CPU and RAM usage. Skyrim spiked at around 70% CPU usage and RAM usage never went above 60% total (my system tends to idle at about 20-30% RAM usage).