Problem SOLVED: I changed the color depth on my video card from 16 bit to 32 bit, tried a test render, and it works just peachy. I'm not sure why this works - I'd have thought that the AVI render was a straight computation process, independent of the video subsystem (it certainly doesn't display anything while it's rendering), but I'm certainly willing to accept an unexplainable fix as long as it works! Thanks to all those who read & replied here or via e-mail, everything must've finally clicked into place tonight.