Have you tried right clicking and opening the properties window for the file? I've noticed that different cameras seem to output at slightly different sizes.

Our camera seems to put out at 720x480, though I've seen 720x576 before as well. I think I would trust what comes up on the properties settings for the file, but maybe capture a couple minutes worth of stuff and try outputting it in different resolutions.

If you're feeling really fancy, get a piece of graph paper and tape a couple minutes of the camera pointing at that, then output it at a couple different aspect ratios. Whichever one doesn't distort the squares in the graph paper is the correct aspect ratio.

It *would* be nice if the software companies would standardize all this stuff