You can enable the driver by editing the info.plist file inside System -> Library -> Extensions -> ATIRagePro.kext (control-click to show package contents) -> Contents. Inside the plist file, move to the IOKitPersonalities -> ATIRagePRO -> IOPCIMatch entry. This contains the boards for which the driver will load. The Lombard's signature is 0x4c491002, and that signature is not listed. If you add this signature, the driver will load after you save and reboot. Editor's note: You'll probably need to edit this file as root in order to save your changes.
Use at your own risk; on my machine, no problems occurred after applying this "hack". Keep a backup of the original Info.plist. Thanks to Luis Flores (no email address available) for finding this out, and check out xlr8yourmac.com for the full email from Luis, where he explains how to find the signature and how to prove whether the driver is or is not loading.

