I have stopped having this problem. Once I do the "Get Info" to load the cover art it has been stable. I have changed the way I have edited the metadata however (including adding/changing cover art). I have started using Subler to always edit the metadata and not do it in iTunes. I read somewhere that for files Optimized using Subler, iTunes has to do some re-writing of the file if you edit in iTunes. And it is slow. Yesterday, I started to do the edits using Subler and it is much faster. Seems like my iTunes art work is more stable too. One thing I learned yesterday, is if I do edit using iTunes, I get the spinning beach ball for a long time and if I go to the Activity Monitor, is shows iTunes is unresponsive. It's not, it is slowly transferring data to the remote HDD. If you wait long enough, it will eventually finish it's edit. However, if you interrupt the process, you can possible corrupt the file.