I make minecraft videos.

I record with Fraps and then convert them to MP4 using Handbrake for editing.

I've never had this issue before, but suddenly after converting the fraps files to mp4, the compressed file is unplayable in any video player (including VLC).

I'm wondering whether its because its on my external HDD that there's an issue with encoding but that's never been an issue before.

Any help is greatly appreciated.