What  don't understand is why ZT says he has lost work through this:
 
"I still save quite regularly but when this happens I effectively lose everything from the previous time I saved my work."
 
The only times I have ever seen this message is right after a [successful] save. More information required I think

I've gotten this error for 1.5 years ever since I got my new computer with Win 8.1. This never happened with Win 7 and my old Layla sound card It still happens sometimes with Win 10. It happened a lot more with 32 bit projects.
 
Right now I only have 1 32 bit project left that's active and even very recently I've gotten it a few times. I quickly hit the spacebar 2x to start and stop. Hit save and it always works fine. Never lost a thing. It's pretty harmless if you use the spacebar method.

Had this "General Error" just now with the latest Update [23.4.0 BUILD 38].
 
I couldn´t save nor save as. It always showed "General Error" and didn´t save at all.
The "Play-Button" method didn´t work for me but I could eventually save my project with "save copy as...". :-)

It's been a long time since I've seen the general error, yet I did see 1 so far with 2017.04 which I very recently updated to. I hope this thing hasn't come back. I hit save a 2nd time and it worked. I didn't have to use the play button method

its possible you can not over write the file because a process is still running (a plug in is my guess).
But creating a new "Save as" isn't over writing anything so it saves no problems.
I would check my plug ins to see if some type of process is running in them.
 
I have seen plug ins dirty projects just by simply being there.