I have a related problem on my 550. After the last upgrade I made, about a year ago, the unit takes great delight in telling me its memory is full, and also that I have far too many way points (in fact I have none) and it wont play any more. If I go into the trip log and delete its contents which are never more than 1%, it may deem me worthy of a route.
Latest game it wants to play is to give me "as the crow flies" directions. Dead straight lines everywhere?
I'd like to take what I can out of the memory and run the SD card for routing instead of the internal memory. If anyone gets the drift of what I'm trying to do could they tell me which of the files, gmapbmap.img,gmapprom.img etc I can delete without affecting the units operation to free up memory space.
many many thanks and a hearty well done if you can understand my cack handed way of describing my problem.