I got a 5870 2 days ago and on boot up it worked fine, but then after loading latest 10.8 drivers and rebooting the display was corrupt. looking as if the refresh was too high. after messing about a bit i removed the DVI and plugged in the HDMI input. The display was perfect. No problems. It was the initial welcome screen that appeared corrupt but after changing the input it looked fine.
After rebooting again , had the same problem with the HDMI port. Changed back to DVI and the display was fine again. So no I leave it on DVI, as it looks better than HDMI , but now i have to reseat the DVI on the card each time i start up or reboot. Another odd thin, this only seems happen if the monitor is powered on at boot time or when i reboot. IF i leave it off until i get to the welcome screen of windows XP (32), and then switch the monitor on then all graphics are fine. All welcome screen icons are available.
video card : Sapphire 5870 1GB
ram : 4GB DDDR2 800 (kingston - no sure if its a problem )
PSU : 650w coolermaster extreme power RS650-pcar e3
mboard : ASUS p5q-vm mboard with only one pci-x x16 slot
CPU : - Q6600 running at 2400hz stepping g0 ( not overclocked yet)
drives: 1SATA 250GB 1 500GB (both seagate)
monitor : samsung 2494HS resoution - 1920x1080
OS : windows xp 32bit SP3
Everything else with the card is fine, except for this one issue. I think it may be the monitor or a driver .. but updated all drivers for the chipset, enabled GPU scaling in CCC, set the monitor to manual source selection (digital)
POST is fine and gfx are fine intil it hits the welcome screen. It looks like the picture is being crunched into the middle of the screen with about 3 inches of black space all around. removing and adding the connector is the current fix . but a real pain to to remove and re-add it each time .
Also removed all the previous onboard intel gfx drivers. Add latest samsung driver for monitor. ( i had no gfx card or 2 years , used onboard only, have to catch up on many games now )