Reinstall the Firmware. It may be that the file you used to install them is corrupted so download a new one and do a manual upgrade. If this doesnt work check the id3 tags on your files as they could be corrupted as well. If neither of these things work search the board for other options, and try them out, there is no one solution beacise it seems there is no one cause,.
The other thing you could do is a soft reset (Slide the power switch up and hold it for 15-20 seconds)
