612 satnav and multimedia console

Hello - couple of naive questions as i'm learning my way round my 612... I have a Kenwood DNX9280BT (multimedia/satnav/bluetooth/etc) unit fitted. I'm not clear whether this is original equipment or retro fitted. Assuming it is original equipment, I wondered if anyone had any experience in rebooting these units? It seems to have gotten itself stuck on a loop of loading up the initial welcome screen, then giving up and turning itself off, only to have another go at starting up a few seconds later - this is a continuous loop and it never gets to the main menu. Its come up spontaneously - it worked fine and then, just didn't. I've tried the reset button but that doesn't seem to work and the trouble shooting in the manual doesn't cover this. Do any other owners have a similar piece of kit fitted? and if so, any tips on getting it restarted. I did the usual "Maranello reboot" and turned battery off for 30 mins and tried again but to no avail. The car is a 2004 model F1A - any suggestions gratefully received!