I could only run in safe mode. I removed the Avast app in Outlook and in the registry. I even disable Avast to see if it would let my calendar start working. Outlook will start and seem to work, until you try and change any appointments that have not happened yet, then you get "can't open this item. operation failed" or if you try and modify it "could not save item. Your changes could not be saved because you don't have permission to modify some or all of the items in this folder". I am on a personal machine and I am the owner, so no exchange server is involved. I spend hrs on line trying to figure it out and low and behold, uninstalled Avast and problem gone!
Update: Everything working good, thought I would take a chance and put Avast back on and back to the same problem. Its Avast putting something in Outlook that I cant find to remove.
I will have to either run in safe mode or uninstall Avast 10.3.225. Thankfully I never paid for it or I would be out the cash.