You may have encoded the files with a codec that is unreadable by your player. This could be due to using a strange format, a corrupt codec or a bad encoding application process (including hardware).
It can also be caused by a bad player.
If your player otherwise works (with other files & types), then I would suspect your encoding process is the problem.
- try reinstalling your application software & codecs
- try another format
- try another application
- make sure you have the processing power to create these files (speed, memory, etc.).
I assume you have created these files successfully in the past. If so, have you made any system changes that may account for processing problems (memory, drives, OS, etc.)?
Dell