no idea if this is possible, but it would rock if
the launcher would set xbmc into window-mode
before launching the application and set it back to
fullscreenmode when the launched program is quit.
the reason is, that almost every application can't open
in fullscreenmode when xbmc is already in fullcreen.
(in fact xbmc does switch to windowmode this way too,
but too late - means after the applications has launched
or after it quits, one of both)
it works fine when you switch xbmc to window
before launching.
i found two threads which are about similar problems
( though i don't have dual-monitor here, but use
"1920x1080" nvidia 8500-GT):
http://forum.xbmc.org/showthread.php?tid=37377
http://forum.xbmc.org/showthread.php?tid=36305
so it seems thats it is a problem in sdl.
edit:
btw gentoo, i686 AMD Athlon 64 X2 Dual Core Processor 6400+ AuthenticAMD here