Picture Freezing And No Sound Problems

Hi guys last night i tried to watch a couple of movies that i transfered to my external HDD via pc using the Dreambox Control Centre,i have had a couple of problems with the odd picture freezing before but nothing to dramatic.

But last night three different movies i tried to watch either froze or played ok for a while then the sound cut off.I tried restarting my box but still the same thing happenened,the films are all mp4.

Anybody had the same problems?

Tried it on usb stick and works fine.Also tried films i tried to watch last night and all ok now very strange?

Been okay for the last week watched three movies without any problems,then last night after around ten minutes sound cut off.
Could it be an hard drive problem?

Yes its a usb powered hard drive. I have actually been thinking of installing an internal hard drive.My son has a Mac pro book internal drive that he took out when he upgraded to bigger capacity hard drive,would this be compatable with the VU