Same problem here and it is preventing me from working, besides threatening to drive me insane. It started for the first time today and, unlike BurrWalnut, I do not have any external memory devices connected.
Update: it only seems to happen to documents that include Japanese text.
Good insight, I now found the bug with your hint.
A short test can verify the bug and the solution as follows:
- open word for a new document
- type in some random characters and stop there, no security window pops up.
- move your cursor (mouse over the characters you just typed) and the security window will pop up.
- look at the opaque window on top of the cursor, it says NOT RESPONDINF and then the security window pops up
What happened is that word is trying to find online translations for the languages listed in the translation box, you can find the languages by clicking the right most icon in that box. There will be two options:
- update
- remove.
I selected the remove option and got rid of all the online translations and this solved the problem. I did not want to put in my credentials and have it send to office.microsoft.com, so I did not select the update.
Good luck to you all