Does the issue occur on older drivers?
Have you tried using Radeon Settings to configure the displays under the Eyefinity tab?
Are you using DisplayPort 1.2 certified cables no longer than 6.6FT long? DP certified cables here.
as you can see - latest crimson drivers are in use )
the length is bout 1,5 (4,9 ft) m long, cables are 1.2 certified yesssss... ))) Sry, but the link is broken or something is wrong (