HELP: Choppiness, but only under specific circumstances . . .

[carshow2]

First, by way of introduction -
AMD 1800
ATI All-in-Wonder Radeon 8500DV
700 M Ram
Windows XP (The Second Coming)
Running pretty lean, I think. No Virus software, or any other programs that I'm aware of (downloaded Advanced Startup Manager, and removed all of 'em)

Okay, so I know I'm not running on anything like the screaming eagles that I see posted here, but the game runs very smoothly up to 10 x 7 resolution, at which point it becomes a little choppy. The problem I'm having is a HUGE (down to a couple of frames per second, I'm guessing) drop in quality while I'm playing the game, accompanied by the computer doing the skipping record thing with whatever audio was being played at the time. It seems to be limited to occasions when I'm looking at several objects (in the example that most frequently came up, it was a couple of boxes, with a candle atop), although I also seem to remember at least one occasion where there were no objects in my view. If I pan the view around (that is, in third person, to look at Garrett), the problem disappears completely and performance is once again tip-top. However, as soon as I pan back, insta-slideshow.

I'm assuming this is simply based on the limited capabilities of my computer, but what's bothering me is that 1) The drop is so dramatic and so sudden and 2) it seems unaffected by the resolution (same on 800x 600 as on the next one up). I've updated my drivers (though I haven't yet tried the Omega drivers, which is my next step), and the only other performance issue I've noticed is that the menu screens (intro screen, options, etc) have VERY choppy transitions. Anyone have any thoughts, other than to look into a new graphics card/CPU/more memory - I'd feel like a real dope if I had to drop another couple hundred to play a $20 game, uber-cool though it may be.

Tony