Yes, this happens even after restarting my computer. The error ID that I sent yesterday was made before restarting my computer though. Should I send you a new one?

Also, this error happens both in a new document and an old document including citations created by Zotero. In a new document, the "Document preferences" window does not pop up in front of the Word document. When I minimize the Word document to find the document preferences window, choose a citation style etc, and click "OK," the error message occurs. In an old document, when I try to add a new citation using the updated version of Zotero, the "Add/edit citation" window does not appear in front either. I have to minimize the Word document to find it. Even if I choose a citation, it cannot be added to the document.

Also, after restarting my computer, I opened Zotero, and the error message popped up. It generated a new error ID: 250270257.

Please advise what to do. Thank you.

Thanks for the response. Yes, it worked by clicking on Firefox in the Dock, both in a new and old documents. But is there a way to make it work without doing so? It's a little annoying to have to go through an extra step for each citation.

This looks like it's a 10.4-specific issue, but it will be fixed in the next update.