Hi Rex,
Sorry to say that it looks like you have a dufunct project. The pds file (altought it is a text file) is long and complicated and nearly impossible to repair. Your only hope (Obi-Wan) is to revert to a previously saved version of your projects pds file (you did save the project using different filenames didn't you? i.e. Project01.pds, Project02.pds etc "saved as" after every change/hour) or if you are lucky there will be a backup version of the pds file (same name but with a .bak extension to the filename.)

Hope all is not lost for you

Kintara Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so.