I wonder if my issue is related. HD4850 on Vista 64 bit, latest ATI 8.10 catalyst driver and also dual monitor. Every time I change games, or the system goes in hibernation mode, I lose the screen on my 2nd monitor (my HDTV). If I try to change the HDTV as my primary monitor, I lose the screen completely and am forced to reboot (mode not supported shows up on my HDTV). I have to play around with the refresh rate in CCC to be able to use the monitor. The HDTV is using a VGA signal but I don't think that would affect anything.
I never had this problem with my older system running an Nvidia 7800GS.
I never had this problem with my older system running an Nvidia 7800GS.