(Booted to Port folder.)
Yep, we've had a few people with the German version of the game experience this recently.
Here's the longest thread on the issue. There was never a definitive solution provided, though you should be able to click Cancel through the error message and keep playing. Let me poke around the Wiki and see if I can come up with a better solution.
Edit: Okay...let's see if this fixes things. Download the attached table file, and plop it in the folder FreeSpace2/fsport/data/tables. You'll probably have to create those two folders yourself.
[attachment deleted by ninja]