just for info.
I bought one of the Medion devices on 28th March. After receiving the fatal error message I fixed it following the instructions I found on here. IT then worked BRILLIANTLY for 2 weeks. I went on vacation, it took me to Ijmuiden, and then from Newcastle to Dumfries. TMC worked well, EVERYTHING worked well, until it died the day after I reached my vacation destination. First it wouldnt find the town I had just reached, then it wouldnt find any maps at all, then it wouldnt start past the first screen.
Of course I ahd the operating system plus maps on the card so I could clear the flash memory and re-install. This went perfectly, but still it wouldnt start past the first screen. Tried re-sets and any number of re-installs, no joy, it was dead. Printed out a route from a PC to get back home.
Aldi had no replacement so I got my money back and bought a TOMTOM Go 910 at the weekend. Shame, it was really good while it lasted. 
But honestly, the trouble it caused was bitter indeed. My wife told me when I fixed the fatal problem to take it back blablabla, she was very smug when it died on vacation.
Medion adieu