Sony Ericsson :: ELM Media Player Not Working?

Since today, it seems my media player is not working. its opening, i can see which all media are there, but the songs are not playing, the videos are too, like stuck. i switched off, removed battery n put it back, no change. i did master reset, no change still. the problem disappears when a call comes(or missed call), it rings. then immediately if i try, media works. once i exit, and retry, its stuck again. same when i change ring tone volume. after i play ring tone, music works, after exit, problem persists.