Not really sure why it would behave like that. To test, have you created a new file and tried opening that? What path is being used to save the files created? All I can think of is for some reason, the program cannot access the requested file when it opens.
What happens if you open the file from the flyout menu?
I was looking for the old style of file associations where you could specify certain operations when the file was clicked, but have so far been unable to find anything but the Default Setting Programs utility.