Was trying to track some graphics to footage, and was doing fine. Got about half way through the track and the analyze button just quit working. I click, and nothing. I know sometimes when it doesn't have data it will quit tracking, but there is plenty for it to track. Did some setting in my footage change or something?
I find that Motion is still very flakey, and things can just randomly stop working - with me, it's usually when you think you're nearly done with a project...
You can try trashing the prefs (which has never worked for me, but it's always recommended as the first thing to do). If that doesn't work, try copying and pasting all your layers into a new project. And if that doesn't work, trash Motion (using FCS Remover - your project and media files will be unaffected) and reinstall it.
This probably isn't very helpful, but you may be having the same problem I have. I often get only a few frames into a Match Move analysis and it just quits. Even when I've given it an area of high contrast to track.