CD doesn't work. LED readout says FRMTREAD, error 12. ;what's happening?

If this error appears on any music CD (burned or store-bought), it's likely the laser/lens assembly is having trouble focusing well enough to read the disc. You can try resetting the unit (use a paperclip or ballpoint pen to press the button in the small hole next to the eject button), but there's only a small chance this will help. You could also take it to an electronic repair shop to see how much a cleaning would cost (usually more than the player).

If it only happens on burned discs, try changing brands of CD-Rs or even burning the disc at a slower speed. If the songs are burned from iTunes, try burning other formats (i.e. MP3) via a different method.