Thanks for your suggestions John.
Yes I've tried every way conceivable, opening it from the desktop, from a usb, from recent files. I've installed, uninstalled, removed Atlas, PC on, PC off and still crashing. Nexum will open, save and reopoen that saved file just fine but will crash when opening files from the previous version.
I have sent the (one of) problematic file to Lars who will test it to see what the issue might be.
Jamie