Tried resetting PRAM? Hard Shut Down (hold power button until MB powers off) then boot up and hold down CMD+Option+P+R and release after you hear the 2nd startup tone... happened to me last week and that fixed it.
I wioud recomend deleting the contents of the user/library/cashes folder. It fixed my shutdown issues plenty of times. I would also recommend repairing disk permissions and making sure that permissions for your home folder are set correctly.