I've been having some trouble restarting and shutting down my iMac. Whenever i try to do those two things, it just freezes and I have to manually restart it. I went to Disk Utillity to repair permissions but Disk Utility also freezes and fails to display anything. I've included a screenshot. I tried booting with the Mac OS X CD but Disk Utillity freezes there also. What can I Do? Thanks.