Another iMAc question about iTunes

I know my iMac is doing it's best to die but apart from taking the best part of a quarter of an hour to boot up another issue has occurred.

iTunes will now only play internet radio stations, Radio Paradise is a url in my artist list or several other that are in Playlists- Radio Stations.

My ripped music is on the server and iTunes sees the music at the correct location but when selected the play icon cannot be "pressed". It would seem that all settings are what they should be.

Any ideas?

Thanks

Howard