As a user of Macs for twelve years and someone who can usually nail most problems either by running a repair app, or zapping pram, rebuilding desktop, starting from a clone of my OS on another drive and running Disk Utility etc etc etc this one has got me totally foxed. I have even tried replacing the main system drive in case it was the HD that was the problem. At the same time I installed 12 gb of brand new RAM. It worked fine for a week and now the problem is back again. This has been plaguing me for months and means that nine times out of ten I have to force shut down with the power button or tug the mains cable out of the back. I don't mind doing this occasionally but I'm sure that this can't be doing my computer any good when I'm having to disable it in this almost every day. It's strange because Restart seems to work quite happily, it's just shutting down that my Mac Pro doesn't want to do. Running Disk Utility often tells me that I have 'Invalid Volume File Count, Invalid Volume Directory Count, Invalid Volume Block Count' or some such similar on a fairly regular basis. This was on the original HD and the brand new one that I've just installed. Any ideas? Any suggestions? Also the Mac chime has decided to become super quiet of it's own accord. Very strange. I'm thinking of doing a clean install but I have absolutely masses of third party software and plugins installed which I don't want to have to go through the nightmare of finding and running all of the installers again. Just installing Logic Pro takes hours on it's own and I simply do not have the time. Would Migration Assistant be the thing to use to help with this if I wipe the drive, reinstall the OS and then 'Migrate' my apps and prefs across from a present version of my OS from my Cloned backup? Any suggestions will be gratefully received and tried out. Kind thanks for listening Steve 2.66 GHz Quad-Core Intel Xeon running OS X 10.6.8