I just got the same error message when installing the Payables 9.2B upgrade at a client site - their Adagio is on the C: drive.
I tried all of the remedies above and still couldn't get past the error message. I was working with their IT person, who is the system administrator.
Any other ideas. We pretty much ruled out "rights" and corrupt file as culprits.
Thanks
Steve
PS - I also upgraded Ledger to 9.2B, no problem at all.