With SnowLeopard, I was using spaces, with two spaces. On the second space, I was running a fullscreen application.
I created a shortcut to switch from my first space to the second space : Cmd+1 goes to space 1, Cmd+2 goes to space 2 (displaying my fullscreen app).
I recently upgraded to Lion and cannot reconfigure it to have the same behavior I had with Snow Leopard :
When running my app fullscreen, a new space (sub-space ?) dedicated to this app is created. Now, when pressing Cmd+2, it displays space 2, but it is empty, as my fullscreen app is somewhere else.
How can I make sure my fullscreen app sticks to a space, so that using Cmd+1 and Cmd+2, I can quickly switch between my normal desktop (space 1) and my fullscreen app (space 2) ?