Well the subject pretty much describes it all, sometime my iMac wont even boot and when it does the desktop is as far as I get nothing is click-able and the only way to get out was by a force shutdown. If I had not down a backup with CCC I would have had to reformat and reinstall the OS and lose everything. I'm sticking with the older version until this is fixed and if I can provide you with any info on my system let me know and I will.