Recently I purchased components to upgrade my 5-year-old computer to give it a little bit more power. I got an AMD FX-8350 8-core processor, Asus M5A99FX motherboard, and a Radeon R9 270 video card to display it all. My original plan was to use that card in concert with my old Radeon HD 4870 video card, but it turns out the latter was too old and the drivers would recognize one or the other, but not both. No matter, the R9 could drive all three of my monitors once I figured out I had to use the DisplayPort for one of them.
The real issue was that often, when I would return to my computer after a time away so that the displays were turned off, I would get the dreaded BSOD an an error from the atikmpag.sys driver (this is on Windows 7). I looked high and low for an answer, but ultimately found nothing. Instead, I changed the power settings so that the displays are never turned off, and that solved the problem.
Maybe newer drivers will solve this eventually, but if anybody has a problem with this issue, adjust the power settings.