I have an interesting update to this thread. I'm using a MacPro and OSX 10.11. I haven't read anything in any other forums about this so I'm assuming it's an OSX El Capitan bug. When I plug in my 6 Dual-Link DVI adapters using the MacPro's USB ports for power, my system was hanging. It would hang for 5 seconds, then "unhang" for 5 seconds and repeat. By chance I plugged all of the USB cables from the Dual-Link adapters into one of those 6x USB power supplies and the hang disappeared. As a test I plugged one of the USB cables back into the MacPro and the hang issue reappeared.... It SEEMS to me that if you connect the Dual-Link DVI's USB plugs to the MacPro you're running the displays off you will experience this issue.
