... So let's focus on your European SD card for a bit. Are you able to see your European SD card with your PC"s operating system.....
I am pretty certain that it does work on my computer when it says "use you device" or something like that. When I turn the tom tom on with European map it just says "no maps found" and I cannot do anything else with it.
That reply raises two questions we need to ask...
I think canderson was probably asking you if you could simply SEE the contents of the SD card on your PC (using Windows Explorer) Knowing what files and folders you see on the card would make a diagnosis much easier.
But from what you say, it sounds like you have tried using TomTom "Home"s on-screen simulator, and that is actually working.
Is that the case?
If so, just try using that simulator, and plan a new route with it and then save any location as a new Favourite. that simple act might be enough to re-write a specific file that is known to be easily corrupted.
If not, go back to Windows Explorer and list as many of the files and folders you see on the card that you can for us please.