Hi Duoro.
Thank you for the suggestion. I have checked my drivers and they are up-to-date. I have a NVIDIA GeForce graphics card. Affinity Publisher was working perfectly yesterday. I can load a file, make changes to it, but when I go to save it, it just closes. I've tried saving it with a different name and when I go to open the new file, I get a message that the file isn't supported by Affinity. (?) I have the latest version of Publisher. I created a new document, opened the document that I need to work on, and have been copy/pasting from one to the other, a little at a time and saving as I go. I can do about 3 saves before it closes down again. Strangest thing. I've never had an issue with AP until now. I hope to find a fix soon.