I have a couple VOB files which are fairly large, so I know there's data in them. When I plug them into VLC and Mplayer, they can both read them, after a fashion.

VLC thinks about it for a second, then plays the file on some kind of super fast-forward: the time index will show it playing 20+ minutes in about 10 seconds, leaping through it. Sometimes it'll show a couple frames of picture as it goes.

Mplayer thinks about it for a lot longer, then does something similar.

I grabbed ffmpegX looking to see if conversion would help with it, but if I run it through to say AVI Divx, it outputs a tiny AVI file that contains about a second or a flash of video. When I drag one of the VOB files onto fffmpegX, the Video box for the file says: mpeg-2, 720x480, 8000 kbps, 29.97 fps. Audio is ac3, 48000Hz, 192 kbps.