Hi Zooster. Sorry to hear about the headache you currently have.
I have had similar problems in the past month, the first time really freaked me out.
In my case, I noticed that some of the files on my sd card know longer showed up, and later discovered that others had indeed become corrupted.
I solved it (and continue to do so when it happens) by formatting my sd card and copying back onto it a copy I have of all the Tomtom files. Infact, once you get it working again, I suggest you regularly make a copy of whatever is on your sd card in case it happens again. For me, it seems
to be ROM specific, i.e. only happens when I flash some of the new ROMs. Sometimes the sd card suddenly stops showing up in file explorer, sometimes I just need to remove tomtom and then reinstall it.
The problem for you now may
be getting the original Tomtom files, I guess it depends where you got them from.
When I flash some ROMS, this problem occurs. I have to avoid ROMs that do that and choose another.
I hope you manage to sort it out. I know what's it like when these things suddenly go wrong for no reason! Best of luck.
Samsung Galaxy Note GT-N7000
Android Version: 4.0.3