Update to the post (Yeah, I know, it's been over 4 months, but it still happens):
-Explosions will not display when the weapons fire disappears.
-Parts of the Vasari Starbase's Disintegrator rays will disappear, before being unable to show anything.
-I have upgraded my video card to a NVIDIA GeForce 9800 GT (512MB), but the issues persist.
-Disabled the page file (the area of the hard drive that is used when you run out of memory, except my comp kept using it when I had at least 2GB to spare...). Other than the game running smoother, there was no effect.
-Again, all drivers are kept up-to-date
If anyone has run into this problem before, or has any idea about what might be causing it, please let me know!!