Recently itunes has started to play up on my macbook.

I was using it yesterday and it was working without any problems, shut it down as usual and today it spends ages 'importing itunes library' before giving me a message about some of it being broken and then it has to reconfigure the sound check volumes. Also, when trying to download some music, it will either stop at 100% and give me an error code or if the same song was downloaded on my ipod touch, it will play fine, until it is synced with my macbook where it will still display the song but refuse to play it. This has only happened on a select few songs, I have tried downloading others and they all work fine.

This also happened when importing a cd, the cd would play all tracks fine, but the two last songs on the cd would not play in itunes, once imported.

Are these common problems that people are experiencing or are these unusual?