Try Ctrl-Alt-Enter to toggle fullscreen mode. This solution was found here: http://ubuntuforums.org/showthread.php?t=918148

2009/9/21 Chengqi Song <songcq@gmail.com>
hi,

i like to use rdesktop -f xxx.xxx.xxx.xxx to connect to my windows pc, in
fullscreen mode. but after entering the rdesktop window, i can not switch out
anymore, M-1/2/3... can not switch workspaces anymore. i have to disconnect the
remote machine to switch out. how can i use xmonad's hotkey inside a rdesktop
window?

thanks
lars
_______________________________________________
xmonad mailing list
xmonad@haskell.org
http://www.haskell.org/mailman/listinfo/xmonad