Update: Still don't have a definitive cause, but I'm pretty sure the problem is with Offices's paste function--more specifically, the (relatively) new version that stores multiple items in the clipboard.

I can't replicate consistently, but it appears that sometimes, when you already have a lot of items in the clipboard, and then attempt to copy text from a non-Office app into Word, Word gets stuck on the previously copied item.

Stephan, regarding your questions:

1. Doesn't matter if you do straight paste or text only.

2. Has only happened (so far) when copying text from outside of Office.

3. If you have the clipboard open when you copy, the newly copied text does appear in the clipboard.

Guessed, regarding your suggestion: I checked, and Windows did not have the multiple items in clipboard enabled. I have enabled it, and will do some additional testing tomorrow.

Thanks for all your input!