Aha. I see it is insert.
So. Close down word completely and re-open it to a fresh page.
Then go to your thread with the offending popup and press the PrtSc Button. Either you will toggle 'insert mode' on or you will silently print the screen to the clipboard. It will not tell you what it's done, or indeed if it's worked. Or if it's switched on insert mode.
Now, to see what it's done, go straight away to word. Click on Edit, then choose paste. Or just do Ctrl-V.
What happens? Do you get a completely different picture? If you do, then click on Edit, Office Clipboard. This will show you what you've got stored in the clipboard - if you've been pressing PrtScr all over the place you might have a load of different images in there.
Tell me what's happening and I'll tell you what to do.