Erratic slowdown issue

[Bipedal]

I'm running PSU on a Vista Ultimate PC at the highest settings. No AA or anything, just the 'highest' option in the settings. I can run just fine at 60 FPS with no slowdown at all for the vast majority of PSU. There are times during fights or when I'm surrounded by enemies that the framerate will drop to 30, except instead of just dropping, everything goes into uber slow motion. Why? Why wouldn't the FPS just go down and give me a choppier performance? Why the ridiculous slowdown? Here are system specs:

AMD Turion 64 X2 Mobile Technology TL-52 1.60 GHz
2047 MB RAM
NVIDIA GeForce Go 7600

I'm running in 1440x900, but I play PSU at 1024x768 windowed.

Also, setting frameskip down to 1 is pretty much my last resort. After playing the game for hours and hours on 0, it's just too beautiful to give up.

So far I've tried lowering the model settings down to the 'normal' levels.

[ZeroVer01]

That's just the way this game engine performs, and sadly, you are not using a very powerful gpu (integrated ftl). Your best bet is to either drop most of your settings down to keep frameskip at 0, or resort to using frameskip of 1. That is about your only choice. I guess, if you wanted to keep the frame rate high, you could always turn off post effects... But anyway,

Your other choice, of course, would be to switch to 800x600

[Bipedal]

Post effects was the best compromise. I don't get pretty shiny weapons or water, but it runs damn smooth. Thanks =/