In the office folder where the Outlook executable resides, there should be a little program called ScanPST.exe give that a shot.
Ditto! Its still there in 2016 and as of 2010 or 2013 it repairs OST sync issues as well instead of having a separate ScanOSTThank God -- I had the same thought but wasn't sure. There had been a file-repair feature maybe beginning with Office 2007 . . . .
I must have used it once or twice in the last 5 years on the same number out of 5 machines. Somehow, never have any more problems with my Outlook files.