Thanks Joyturkx, but my 4350 Max does not have a micro SD card (internal memory only), and anyway, I can't see anything in the instructions about "rom update".

I've reloaded the original "OS" from a backup and just updated the device with the newer maps/nfs/poi, and that seems to work OK, although no doubt there would be more features available with the newer "OS".

Unless anyone has any ideas, I think I'll just stick with the original installation with the newer maps.