Installed 2 5870s.
Left off the left side panel of my case(cooler master haf x), started my computer, installed the drivers and set up the crossfire... yada yada yada... everything worked fine.
Then turned off computer, put left side panel back on, turned on computer, and heard a very loud buzzing (asssuming it was a gpu fan). Checked status of cards (in Windows 7) and the secondary card did not appear.
Turned off the computer, took off left side panel, jiggled power connectors into secondary card, then turned the computer back on, and it worked again. Put the panel on, turned on computer, worked.
Sometime later, turned on computer, and there's that loud fan sound again. What gives?