Error when opening Stadium Solution file

I have a Stadium Solution file, and when I try and open the file I get this error below, how can I fix this so I can open the solution again

Thank you

Hi Brian,

Which version of Stadium is this. I have experienced this before and a restart of the computer helped. If not, please email me the solution file and one of our Dev team can open it and save it for you to open again.

Best regards,

I am using this version:

I have send a copy of the solution to @anton.platzoeder, but I will also send you a copy.

Thank you