After eliminating the power supply as the overclocking issue, I realized another concern I'd had. My HIS 4890 was not immediately recognized by Rivatuner. I had to use the patch from the link below. The patch was made when the 4890 had just come out, but shouldn't it have been supported by Rivatuner by now? Is this a normal thing to have to do with Rivatuner 2.24c, or should I think this is an odd occurrence?
http://www.guru3d.com/article/overclocking-the-radeon-hd-4890/2
http://www.guru3d.com/article/overclocking-the-radeon-hd-4890/2