MBP '07 model... framerate issue?

I know this has been addressed many times, but my partner and I have searched for solutions and we can't find a perma fix.

She has a Macbook Pro from 07, NVidia 8600M GT, 2.2 GHz C2D processor, with 2 gigs of DDR2 memory clocked at 667 MHz.

At first, SL ran very smoothly. However, once the game has been running for a little, the framerate plummets immediately. Not like a gradual decrease, like one would expect after objects have been loading for a while; it's an immediate and sudden plummet to around ~10 frames, even in places where there are few people or objects. And what makes it weirder is the fact that every now and then, the framerate will jump up to a smooth rate, maybe around 50 or so, for a couple seconds, then drop back down.

We have VBO disabled, we uninstalled it and reinstalled it AFTER updating to 10.5.7, we have graphics all at the lowest setting.

I would like to know if anyone has any suggestions or solutions.

P.S. - I have a WinXP SP3 computer at home, with 1G of RAM and an NVidia GeForce 6600. This computer has been slowly decaying and won't run graphical applications very well, be they games or programs. With both this PC and my partner's MBP on the lowest settings, this PC runs SL better than her MBP does.

You might want to try the following:
- Bin your sl client
- Put a fresh one from your download in the application folder
- Now run and enable VBO (if it wasn't enabled already)

If that doesn't help, try coolviewer from hyang reflections.

I'll try this "cool viewer"... that procedure didn't work the second time around either.

Just out of curiosity, what makes the viewers different? I understand when one says "download Second Life", one downloads a viewer made by Linden, and I was wondering how many others there are and what their purposes serve.

Edit: Cool Viewer runs it without slowdowns. Many thanks, Virgo. =]

SCRATCH THAT LAST MESSAGE.
...For some reason I keep getting a 404 error when trying to edit that post. I have no idea why.

Anyway, I started it up a second time to see if VBO was enabled, and it started slowing down again.

It vexes me. It's not a gradual slowdown like one would expect from loading stuff; it's an immediate effect that goes away from time to time and then returns.

EDIT:
I had someone in-game tell me it might be a memory dump issue... would anyone be able to assist with this? I know very little about memory dumping on PC, and I dunno if it'd be anything different on Mac.

I have a similar system and I run Snowglobe with VBO and FBO enabled with Apple OpenGL multithreading. My other settings are around the middle with basic and bump shaders enabled. I also have impostors and hardware skinning enabled as well using local lights. Particles limited to 512 and post processing (glow) on low. Runs very smooth and looks pretty good.

For FBO it's in the debug settings under RenderUseFBO, and OGL multithreading is RenderAppleUseMultGL.