My Acrobat 11 quit editing links after 4 days in a 7MB file, it now only produces ineffective links

My Acrobat 11 quit editing links after 4 days of work on a 7.5MB file and it now only produces ineffective new links (they only look like links in the "Add or Edit Link" mode, they cannot be selected by clicking a corner as the manual says, and they don't go anywhere in the "V" or Reader mode), how can I finish the job with a tool that suddenly became defective?  That mode works fine with a smaller test file, though, and everything I could think of in my Windows XP computer looks OK, including 10.9GB of hard disk free space.