Back pain from long hours at the computer used to be one of the items on my checklist of issues. Since buying my Herman Miller Aeron Chair, adjusting my workstation, and getting a break reminder program (Albion Stop Now), it's thankfully become a non-issues for me. (Don't worry, I still have other issues to complain about here).
I know there are quite a few folks, though, who are experiencing back pain from working long hours in a sedentary position. Here are a few articles and news reports worth browsing for tips: