Is this the one where you get sakura and midori in the menu?
If so, I believe that your ~/.config/openbox/menu.xml is copied from a wrong skeleton.
The relevant files are /etc/skel/.config/openbox/menu.xml or possibly /etc/xdg/openbox/menu.xml.
This happened to me some months ago and unfortunately I can't remember how I fixed it. I think I just copied the proper file from an old account.
Or maybe I just deleted ~/.config/openbox/menu.xml?
Sorry for the vague reply.
MOD! Ha! I think I found it. The correct one is in /usr/share/lxde/openbox. Just copy that (after checking it of course) over your ~/.config/openbox/menu.xml and then relogin (I dont know of a way to reload the openbox menu on the fly.)