Thank you everyone who replied, much appreciated. I have learnt the folly of my ways. Garmin will not let pre-boot mode load (at least on my unit) if I try to do it within 2 minutes of the previous attempt. I just waited a lot longer than 2 minutes and managed to get pre-boot mode to load every time by touching the top left corner of the screen.

I have another question and maybe this belongs in another thread.

The 3490LMT does NOT come with eco-route, if I was to get the 3490LMT (just for the faster processor - because 3d terrain rendering is sluggish on the 3790), will I be able to copy the eco-route files from my current 3790 onto the 3490? Reason I ask is the 3490 does not have EcoRoute (unless you buy it) but when I upgraded my 3790 FW, it still showed I had ecoroute. Which means I should be able to copy some files over.

Does anyone have any clues to point me in the right direction?