Ubuntu Gnome Edition 13.04 problem with external Monitor

[klinge01]

hello

i have a ThinkPad R61i that i use in school on different beamers.
i use the standard Ubuntu 13.04 with unity and the gnome edition (preferably gnome edition because it uses less resources, on my rather old laptop).

i would like to use two different monitor setups and to be able to switch between them without fideling about (like logging out an in etc.).

first laptop and beamer with the same windows visible (mirrored)
second the laptop as primary monitor (with different programs running) and the beamer as extension only the libreoffice presentation visible (non mirrored).

this worked fine before i installed the gnome shell. since i use the gnome shell i get funny behaviour, all open windows get transferred on to the beamer, when i open a new program it stays usually on the laptop, if i open a new window of an allready running program it opens on the beamer.

somethimes i can solve the problem with loging out and in again. and i can solve it as well with changing the primary monitor to the beamer and back again.

does anybody have an idea how i can set the monitors, so that the open applications stay on the laptop in non mirrored mode?

thanks for any help

klinge