I suggest you disconnect the battery, step on the brake, wait a couple of minutes and reconnect the battery - see if the radio will right itself.
Plan B, check the appropriate fuse(s).
Plan C, try a different SD card.
Plan D, wait till someone comes along who knows what they are talking about -
humfrz
PS - you may consider posting over in the electronics sub forum:
http://www.ft86club.com/forums/forumdisplay.php?f=27