Thank you all so much for your replies, and particularly for the original question. I've also been encountering this issue, and the onset of it was also exactly yesterday. Had I not found this thread, I'd have uninstalled, hoping that a reinstallation would be clean and sort the problem. You've saved all my boards! Thank you!
I paste mainly images into my whiteboards. I've been working around this glitch by saving images and then inserting the image files. This still works, but it's not as efficient as pasting in from the clipboard, and doesn't help if you want to paste text in, either.
Thank you again for sharing your experiences publicly. Resetting hadn't worked. I was on the verge of uninstalling, and would have, if not for all of you.