As it says on the tin.
I have a 7870 which is connected via DVI to my monitor. Works fine. But if I plug a TV into a HDMI port the monitor display is diabled and I get no output there either.
Now if I boot my machine with both connected I see output until it finishes loading windows and then both displays go black.
Now I assume this is a catalyst driver config issue. Now i've tried to reset this to default by using the reset to default in the catalyst control center (in preferences) but this does nothing.
What do I have to do? Uninstall the drivers completely and start afresh?