You can't fix this, it's a problem with the player. If it's under warranty GPX should fix it, although after you pay shipping and token fees it may be just as cheap to buy another. Mine worked fine for a while then started doing this. Reviews on other sites reflect the same problem.
This is pretty close being entirely sealed so there is very little the consumer can do when it stops working. (If it ever does to begin with)
Jim, July 2007