I had a look in the MAC 550 manual to see if there was any error messages that are #### and there are none. However I looked in the MAC 500 manual and found that there is a message saying: ****. this could be similar. The **** massage means that there is no communication between the mother board and the control panel. So it says to check all fuses, check the cable between the motherboard and the control panel, and also to re-install the software. This says to me that it could be a motherboard problem...? I would try the above anyway, as for re-installing the software you need an uploader, stage electrics will definitly have one. There is instructions on how to do it in the manual. keep us all posted! hth joe