Why I am getting error while playing videos from gallery app in my Sony ericsson p910i phone?

One of the few things I’ve had issues with is video play back from the gallery. Sometimes it works, sometimes it does. This occurs with both the stock video player and Moboplayer. I have screen shots of the errors I get. I haven’t noticed any pattern about when which error shows up etc. The videos I’m playing are in MP4 format. So what causes this error in my Sony ericsson p910i phone?