I have been working on this particular project all week.
There are 3 parts.
Twice this week one of the parts "Failed to open project".
Luckily I had made a render of it earlier today but now I want to finesse it and cannot because it "Failed to open project".

Any ideas...anyone?  The file is about 86 mb in size.  Is that an issue?  I have 12 GB of ram and 2 GB on my video card. 
I've restarted, and even rebooted.  No joy!