Songs stuck in Automatically Add To itunes folder
iTunes will put any songs that aren't compatible into a Not Added folder (underneath Automatically Add).  If your music wasn't compatible then you would find them in the Not Added folder.  So it seems that they are compatible, just not getting deleted. 

I would check the permissions on these files and see if iTunes has permission to delete them.  Command-i on the files and folder concerned and ensure your use can read and write them.

Another solution is to open the Console.app application (found in the utility folder in Applications) and observe the output of that whilst iTunes is adding the music and see if there are any specific error messages that may point to why it isn't deleting the files.