Hi Nubz N.,
Thank you very much for your try to help me out! I tried to fix the problem that way, but unfortunately iTunes Store did not even let me to create a new account. Every time I try to connect, it says: "please make sure that the date of your computer is correct amd that the cookies from iTunes Store are accepted" (this may not be the literal wording; just a rough translation from German).
This is so weird, because on the front page of the iTunes Store, I can even see my Apple ID and also the correct money on my account. But then iTunes keeps asking me to enter the password in order to allow the automatical downloads. Also, when I try to see my wishlist or when I try to buy something, I seem not to be connected. So how can that be - I am kind of logged in, but not fully logged in whenever I try to use the store?!
However, I tried already to settle the date issue by dating the date & time settings at some point into the future and then putting it back by using the default setting. Then, I added manually iTunes to the firewall list. But this didn't help either.
Mac App Store, however has no problems at all and works just fine. I can enter my account there and everything. Something seems to be wrong with my iTunes or the store. Actually, what I'd really like is to downgrade it back to iTunes 10, because back than I had no problems at all...
Do you have any other ideas perhaps?
Thank you so much in any case - it's already nice that there is somebody out there taking up the concern and accompanying me!
Best!