ITunes doesn't add tracks

[Nadziak]

As I said I have Itunes 9 running on my MacBook and suddenly I cannot add any songs to my Itunes. Before it happened a"click" was enough to add a song. When I click on an mp3 file Itunes does open but doesn't add it. I tried adding mp3 to the library and Add file to the library but nothing works Could anybody help me? Today I bought a CD and Itunes does import all of tracks from CD but still doesn't import mp3's from hard-drive