Q: Why won't video download to my ipod touch?

It might not be the right type of video file. If you are downloading off your computer, is it already on itunes? You might be able to go on itunes on your ipod and download it directly since it has already been purchased.

iTunes: Frequently asked questions about viewing and syncing videos

iTunes: May be unable to transfer videos to iPhone, iPad, or iPod

iTunes: Sync purchased HD videos to iPod or iOS device

If you have a 3G or older iPod only SD videos will sync to the iPod.

I'm having this problem too. It started recently. When I connect my iPod Touch and try to move a handbraked-video file from my computer to my iPod, it tells me that the file won't copy because it can't be played on the iPod. Could this be connected to the latest version of Handbrake? Strangely enough, my older handbraked files are still transferring to the iPod, but ones I've handbraked recently will not.