Re: URGENT! 7600CS (rev 02e1) stays black when screen via VGA extender
You do not have this problem with the 6600?
My experience is the same for a 6600GT with 2 displays connected, one via DVI and the second via a DVI-VGA adapter to a VGA TV.
When the TV is off during X startup, the driver complains (in the logfile) about the display not being connected and does not initialize that port. When the TV is turned on later there is no picture. The windowmanager is informed that there is only one screen, not two.
So, the siituation does not seem to be 7xxx-specific. Maybe there is a difference in the driver version or details of the configuration you use for the older cards?