Can't open PPTA after reverting to Studio 09' from 13.

Hello,

I recently took part in the Studio 13 beta, but I was forced to revert back to Studio 09 in order to make edits on a series of older modules. Unfortunately, I think the revert caused some issues on the back end and I am unable to open any PPTA files with Presenter 09'. I can see and access the ribbon, however, when I try to Open Engage or Import Audio I get an error in the scope of "Presenter was unable to open project file". 

I tried the tips to recover corrupt PPTA files, but had no luck. I ensured that I completely removed Studio 13' and reinstalled Studio 09' a number of times in an attempt to repair. Still no luck.

I passed the files along to a colleague and they were able to open the file fine, so I am reasonably confident it is my system. 

Any suggestions?