Strange desktop behavior with opening of folders

[YAOMTC]

I'm using Arch Linux with LXDE on my Eee PC. For some reason, after some past update, PCManFM seemingly failed to open folders on the desktop when I double-clicked them. At some point I figured out that if it has a window open already, the folder I try to open will open in a new tab, but it won't work if a window is not already there. If I terminate pcmanfm and run 'pcmanfm --desktop' from the terminal, the problem is gone. (Of course, I can't do this every day!) Strangely, if I do the same command from the Run dialog, the problem is still there -- it only goes away if I start pcmanfm --desktop from the terminal... Any ideas?