Hi Steve, sorry I cannot offer a direct solution to this particular problem, but would suggest, for troubleshooting purposes, downloading & installing an alternative Media player(s) to see if similar problems occur with them as well.
Some good freeware alternatives are: 1. RealOne Player - click here . 2. Musicmatch Jukebox - click here . 3. Quintessential Player - click here . 4. Winamp - click here . 5. Zoom Player - click here
Let's know how you get on. Good luck, G