istage mp3 player was working, but now after filling w/music "disk empty"?

1 Gig istage MP3 player, worked while half full of music, then I added more so there was only 40 Mb left of free space- I turned it on and it said "disk empty"...no more list of songs when plugged into computer, but still shows that the memory is almost full. How do I repair it? If I reformat, will it lose the programs that make it into a music player and FM radio? It is a "flash drive" type with a small window to read on top, model IS-2002?