For anyone with a card in these series it is well documented that there are driver issues causing flicker, black screen, and vertical lines (of predominant screen color at time of crash). Here is an ati/amd forum thread on the topic - http://forums.amd.com/game/messageview.cfm?catid=260&th...
My own problems with my 5770 were just about worst case scenario as far as I could tell. I spent the past week scouring the internet for a solution to these problems and finally succeeded.
The issue with these cards is that the voltage drops whenever we exit a 3d application to go into a 2d one. Problems with flicker seem to be prevalent on the windows desktop no matter what, but do not cause the crashes as often as the games do.
To use his tools, Open as Administrator, right-click and go to the 'Hardware' menu then overclocking settings. Look for voltages pull-down menu box and notice that there are two listed. Mine had something like .7 and .95 listed. As MadIO pointed out, the .7 seems to automatically cause the flicker. The higher setting stabilized the card.
Keep in mind that this will not solve the driver issues, and that we are all waiting for ATI to release the next Catalyst drivers. This 'fix' sets the voltage at a fixed default and does not allow the card to regulate it's voltages to conserve power. Theoretically, we want the card to be able to conserve power, but right now there is something wrong with either the lowest setting on the card and/OR the state change is causing the card to wig out.
Please be aware that changing voltage settings can damage the system so if you are not comfortable with using this hotfix then wait for the new drivers to be released instead.
notes: My board (MSI 790FX-GD70) seemed to have issues with HDMI audio too that caused problems in-game even after I got the video card stable. I simply switched out the HDMI cable for the Realtek HD Audio one instead (my board gives you the option of which one to use.)
note2: I also set my game resolution to the same as my windows desktop to minimize the stress on the video card as it changed resolutions.