Micrografx Designer 7 Files

Consistent with my advanced years...I am still using Micrografx Designer for various projects and have just tried to access a number of older files and get an error message saying the application can't access the files owing to an I/O problem.   Other files of the same vintage or older, open just fine.  

I can only suspect the problem files are corrupted in some way.   As they are quite complex, I am loathe to shrug my shoulders and start re-creating them from scratch.   Does anyone know of this problem and/or a file repair program that works on M. Designer files (extension .dsf)?

Cheers,