iTunes won't add or import new files
I am running mountain lion 10.8.2 and my system is fully updated.I have my itunes library on an external drive but I am unable to add new files to iTunes. I have tried dragging and dropping and the plus appears and when I release the files I get the color wheel for several seconds but it does not get added. The same happens when I try going through the menu and cmd+O. I can download new items from iTunes but nothing can be imported. I am at my wits end and can't figure out what is going on.
MacBook Pro (Retina, Mid 2012), OS X Mountain Lion (10.8.2)