Sorry if posted already but if not here you go.

AMD/ATI Releases Hotfixed Drivers for 5800 Series Video Cards

Those lucky few owners of ATI’s new Radeon HD 5800 series video cards, may find themselves in a bit of a bind if trying to install the latest Catalyst 9.9 drivers, as it does not officially support the Cypress series chips yet.

As such, this morning AMD has opened up a hotfixed driver package to the public, to tide owners over until the release of the Catalyst 9.10 which should bring full compatibility under one driver. The fix is intended for Vista and Windows 7, available in both 32bit and 64bit flavours. It supports both the HD 5870 and HD 5850
SOURCE: www.hardwarecanucks.com

It can be downloaded directly from AMD here:

http://support.amd.com/us/kbarticles...icsdriver.aspx