"next" track > first (!) track of Library

Hi all,

whenever I import new music into iTunes 11, it won't play the 2nd track after the 1st, but it plays the first track of my entire iTunes Library. Both automatically and manually (when I hit "next").

When I hit the 2nd track manually (by double-clicking), iTunes advances normally.

Am I the only one with this problem?

Thanks a lot!