SMAH has pointed you to the Pst2gb.exe I referred to, thanks SMAH.
What I had to do for a corrupt pst that exceeded 2gB was run the pst2gb program that corrected the problem.
What I did for a corrupt pst that had not exceeded 2gB and was not fixed using scanpst.exe was the following.
Created a new pst.
From the corrupt pst I dragged and dropped folders to the new pst (actually I did this for a few large folders just to free up some space on the corrupt pst. the file was so corrupt or full it would not allow me to delete files or folders)
Finally I did a "compact now" on the corrupt pst and after about an hour or so of compacting, the pst was restored.
Hopefully you will be as fortunate.
The person I did this for now follows the two golden rules of pst's 1) keep them well under 2gB and 2) store them someplace where they will be backed-up frequently, preferrably on another hard drive or file server.
much luck