Have you tried re-loading the video onto your iPod, by
deleting it off, then syncing it back to the iPod again?
The first thing to probably consider here is the format of the file. What is the format?
To find out, connect your iPod to your computer, right-click on the video in the iPod's library, click on "Get Info", and under the "Summary" tab you should see the type of file.
Also, if you're iPod's space is now full, or very near being full, this may cause it to be freezing up on large videos or any videos as a general, if that's you're case.
If you've tried several different things and they don't seem to work, you may want to try restoring the iPod now:
How to restore your iPod
-Kylene