Same issue, took it into Audi and they came up with some bs about these things just happen. It cost me £200 to fix a year ago. Now my original DVD is unreadable but the Europe one is fine and reads ok.
Audi said my DVD was scratched and it will need replacing. I did try to argue that it didn't make sense as I'm not in the habit of interfering with the disc and couldn't understand how the disc could get scratched.
Anyway long story short, I agreed to get it replaced.
And guess what? they ordered a new disc and put it in and it was still unreadable. They can't explain it and now suggest replacing the entire unit. I had to just walk away from the Audi centre to calm myself down.
Alex
April 2011