I have this issue with my Epic 4g for the past few weeks. Although I may not get that error message....ringtones, recorded video, youtube video, internet radio are also affected when this happens. Everything I've tried so far hasn't fixed it. That includes alternate music players, SD card format, and a factory reset . Today I uninstalled Advanced Task Killer to see if a bug in it could be making it happen. I've had to restart up to 3 times in a day for it to be a useful phone.