well I did try "-i -g -t" but I think I just rebooted and didn't do "openbox-menu --reconfigure". I just changed Bonsai the same way and used "openbox-menu --reconfigure" but I had to reboot Bonsai to see the change. beats me 
LKJ : not "openbox-menu --reconfigure", but "openbox --reconfigure". I try to explain : menu.xml is a file belonging to Openbox. openbox-menu is a program which is optional. It's only feature is to pipe the menu files contained in /usr/share/applications which are used by menu-cache (from Lxde project) to display the menus (and in other desktops, used by the menu manager of Gnome, Xfce, or Kde menu manager... )
So, in Openbox, there are not dynamic menus. Originally, the users would reconfigure the set of menus by hand, one by one each time they installed or uninstalled an app (how boring ! ). The came obmenu, a little better : the Openbox users could edit their menus manually one by one each time a new app was installed or removed : but in a gui ! ^^ What a progress !
Then came openbox-menu. It is shortly after that I decided to switch from Lxde to Openbox only.

So if you modify menu.xml, or rc.xml, do "openbox --reconfigure". Forget about openbox-menu, it is not concerned.

and "Openbox Menu Editor" was spelled "Obenbox Menu Editor". I fixed it. 
edit: I just installed obmenu into Bonsai and it's misspelled there also.
apparently it's been wrong since 2010. 
Oh ?! Maybe would you want to point to this at the software section ?
Have a nice end of day,
Mélodie