Long time Calibre user/ now Calibre will NOT start

I've used Calibre since 2012, never any problems.
I tried to startup the program today and at first I got a pop-up saying there was a problem. I've now tried everything I can think of with no effect. When I try to open it, it now starts to load then shuts down.

Any help would be great!
I've:
Updated to new version.
Ran compatibility test.
Copied files & renamed Calibre book folders.
Deleted all Calibre programs and re-installed.

Pulled my hair & screamed!

Please help!