I've got the exact same problems. I've tried everything I could think off, but I am at wit's end.
CD Driver works fine, but its Catalyst 13.6, not really made for the R9 280X, but 13.10 and 13.11 b9.5 wont let me get past the "Windows is starting" part. It's black screen after that with my screen still on.
I tried 2 PCIe slots. Different Screens. Installed Service Pack 1. Updated everything. Reinstalled Windows 7 and uninstalled everything. Flashed my BIOS ( Gigabyte GA-X58A-UD3R ). Checked my ATX Plugs, but everything is fine.
When I tried to install Catalyst 13.11 b95 my screen turned black and the sound of "Hardware Removed" played.
I hope somebody can help us.