No, tested on ubuntu and fedora. I personally use Sabayon. SAME issue!!! I've got crossfire working perfectly on my HD6870s, on my desktop with the same distro. Its all gentoo. Sabayon= simplified gentoo.
After rotating through distros desperately, I stayed on my favorite (Sabayon). I dont even have Windows on this machine. But Ive checked online with other owners of the same setup and they can enable crossfire in windows 8 just fine using the same settings I am.
I've got another HDD lying around. I'll install win7 temporarily and see if it works.