ok,my friend, on his notebook (so, different PC) found out that a directory he had under my documents, containing MP3s, called "Music - Temporary", is also empty, and it also contains a iTune-related file (more on that. I am waiting to see this file). No harm done, this time, since those MP3s were, as the directory name suggests, just temporary copies from his main collection.

So, what is going on? Has anybody experienced something similar? I can't find any reference to similar problems, on the internet...