I would echo what borisb said.
I have had no trouble playing mp4s. I transferred video from my TiVo to my laptop, then converted the video for apple iPod. I saved that to USB, popped it in the eDGe, and everything played fine (though a tiny bit grainy). I had no video halt or sync problems.
Though, now that I reread my post, I'm intrigued that I only use technology with non-standard capitalization.