ITunes For Mac :: Exclamation Marks Show Up But File Is Not Missing?

After upgrading my iMac to OSX 10.10 suddenly thousands of the songs in my itunes playlists have an exclamation point in front of them and they get skipped during playback. I can play them by simply double-clicking on the song, this will clear the exclamation mark and start playback. I can also clear the mark by selecting the song and choosing "Get Info"—as soon as the info window opens the mark disappears. Once the mark is gone the song then behaves normally and plays in the playlist. 

It has nothing to do with deleted files. No files have been deleted. Itunes never asks me to locate files. The files are inside my itunes folder as they always were.

I have not synced with any devices. I have never synced itunes.

I doubt it has anything to do with itunes Match because I've never used Match or subscribed to it. 

It appears that the only way to fix this is to doubleclick on every song that has an exclamation mark. That would take hours to do. 

A few days ago upgraded my macbook pro to OSX 10.10 and it has exactly the same problem.