UPDATE:
After reading a few other threads were others were having a similar problem I tried what worked for others and it seems to have cured my reboot issue!
I booted in Testmode and deleted the following files (in this order): gpspara3.bin, gpspara2.bin, gpspara1.bin, and gpspara0.bin
Went for a quick 10min test drive and used the Nav functions (including setting a route) and all seems to be working fine.