hi christian,
another try would be to set the driver defaults in catalyst control center first, then enable only accelerated hardware mode in Rhino. Do not enable Antialiasing on boths sides.
I`m using an older driver with HD7970, below are my slightly tweaked settings in the driver defined as custom profile and the rhino settings. I´m sorry if this is all trial and error.
You mentioned the display flickers only if you draw something. Do you get the flickering right after you´ve envoked the tool, eg. the _Line command? What happens if you start the _Line command and just hover with your mouse over one of the four viewports without drawing ?
If you maximize one view, or close other views does it still flicker ? Is this problem present in all display modes eg. Wireframe, Rendered etc ?
btw. make changes in CatalystControlCenter while Rhino is not running. If you could record the flickering this might help the developers to pin down the problem further.
c.