I'm not sure what I did, but suddenly menu buttons are only working as dropdowns (they've lost their single-click functionality).
For example, in the standard toolbar, it used to be that I could click the save icon and the part/assembly/etc would save immediately. If I wanted to choose save as, save all, or publish, I would click the dropdown arrow next to the save icon. Now, I get all of these options every time I click the icon.
This screenshot shows the hover-over behavior. You can see that there is no longer a divider between the save icon and the dropdown arrow (new, open, and print used to have that line as well).
Thanks in advance for the help!