Lightroom 4.3, Mac OS X 10.7.5
Maybe I'm just going crazy today, but working in the Library module, I could swear I used to have the Catalogs, Folders, and Collections panels open at the same time. Now, for example, I have Folders clicked on. So, to reveal the Collections panel, I need to click on the arrow to the left of "Collections." So I do. And Collections opens, meanwhile automatically collapsing Folders. If I click on the arrow left of Publish Services, it collapses Collections, and opens Publish Services. "Navigator" is the only panel I can keep open while one of the other ones is open.
Does this make sense? Did I accidentally hit a key or mess up a preference or something? I just tried moving into a different catalog, and I also updated to 4.3 (I was on the previous version when I noticed this problem this morning) but the problem remains. Am I missing something really obvious?