OK, here's the deal: I ripped Phantom Menace using DVD Decryptor, and then duplicated the VOB file and re-tagged it as an MPG. I also trimmed down just a little bit of the VOB using MPEG Streamclip and renamed it as an MPG and tested it in After Effects, and it worked fine. But then, when I imported the fill movie, it looks like crap. Compression artifacts, grain, every problem up the wazoo. I have no idea what the problem is, since theoretically the only difference between the big file and the small one is size.
Anyone know what could be the culprit here, and what I can do to fix it? Like I said, when I used just that small clip earlier it looked fine, but when I worked with the full movie it looks worse than Youtube quality.