Unable to add card to one board in browser

Annie Carter_xtm453

On one of my Trello boards, when I click "Add a card" at the bottom of a list, or if I select  "Add card" from the menu of list actions, the "Add a card" button disappears, but no new card is created. Here is a screenshot of what the list looks like after clicking the button:

I am having this issue in all lists on one particular board when I run Trello in either Safari (both normal and private windows) or in Chrome. I am not having this issue in other boards or on this board in the iPhone app.

Annie Carter_xtm453

It turns out that I was only unable to add cards to some of the lists on that board, and the other lists functioned as expected. I tried adding a card to a working list, and dragging it to the broken list, and now I can add cards to that list! The other broken lists remained broken, but I can fix them in the same way. But it doesn't seem to be enough to drag any card into a broken list; it only seems to work if I drag a newly created card in.