Hey folks -
I'm working with Excel 16.78 on the Mac and I have a worksheet with a few drop-down menus for their cells. All created with the Data Validation tool. The drop-down arrow appears and works fine. The list appears when the button is pressed. But the numbers in the list aren't shown on screen. They're there: if I select one of the "blank" entries in the list, Excel puts the number into the cell as expected. But I sort of have to guess which number is where on the list.

Even the scroll bar in the list is showing.
It's the same way for all four of the cells I have data validation set up in. And the funny thing is: if I hand this file to someone else, they can see the list fine on their own Excel installation.
Troubleshooting: I've deleted Excel off my Mac and re-installed it. That didn't seem to help. I'm sort of stumped as to what else I might try. Any suggestions?
Thanks!