I once moved a machine from one room to another and had the cash box key laying on the reel shelf ...the key slid down and wedged itself on the board behind the MPU ....machine gave me the same error when I turned it on ....didnt fry anything ...removed the key and turned the machine on the error was gone ....I thought it was wierd but it worked for me .....I dont know if you have moved you machine,but I would check if anything has been rolling around or something got disconnected at that board......Just a thought
Eric