You need to install quicktime pro. Someone recently said it came with Vegas 5.0 but I don't think that's really true. I went to the apple site and bought it. It isn't much money.
I'm a little unclear on the "comes with" vs. "buy it" question. Vegas 5 requires Quicktime. Presumably Quicktime Pro. Certainly quicktime Pro if you want to make quicktime files but maybe just the quicktime player if you just need to read them.
I know I haven't entirely answered the question. Buying the pro version should settle all your problems, whether you use V3, V4, or V5.
Another way to put it is that even after you install quicktime you may still need a specific codec for the file your camera is making. I'd think the manufacturer could supply it.
Buying the Pro version isn't necessary; the free version has everything you need. However, when installing it, do a custom install and install everything including "authoring components".