Two display with different resolution --> Black screen

Hi everybody.

that is my configuration:
frodo (but the issue happen also with other skins) + ati + standard vga display + hdmi projector full hd.

the main display is the vga low res display, and when I switch the projector on my sistem automatically cut signal to the vga display and give signal to the projector. the problem is that in this case, if xbmc has been started before turning on the projector, remain with the vga resolution of the vga display. then if I close and restart xbmc it get the 1080p resolution of the projector (that is the first problem)

now, after have restarted xbmc it get the true projector resolution. if now I turn off the projector, my computer cut the signal over hdmi to the projector and give back signal to the vga monitor but now it get a black screen (I suppose because xbmc has in memory the full hd resolution of the projector and cant map it to the low resolution of the vga display). if now I press "\" it goes in window mode and it show me xbmc correctly but if I press it again it goes again full screen giving again black screen. If now I close xbmc and restart it, it work perfectly using vga resolution of the vga display...

I think it is a bug of xbmc that do not get the updated resolution when it change the display...
any other idea?