Mac Textures / Models Glitch

[Soulforge00]

I have been having some strange graphical glitches happen:

- Some textures do not look like they're supposed to. They will often be a flat, bright sort of off-white color, as snow fell on the ground. Sometimes a particular object (like a car) will be partly glitchy and partly not. See the screenshots below.
- Instead of being nearly invisible, Stalkers are easy to see. They are sometimes seem to be made of "liquid metal."
- The flashlight's beam will illuminate a square-shaped area.

Here are some screencaps of the glitches:


Odd texture on most of car and on ground:

Easily seen Stalker:

Square flashlight:

If anyone could shed some light on how I might address this glitches, I'd appreciate it.

Thanks in advance!

Mac OS X 10.5.8
2.2 GHz Intel Core 2 Duo
2 GB 667 MHz DDR2 SDRAM
GeForce 8600M GT