GPU clock / Memory clock always at max value

Hello,

I'm having a problem with my graphics card, a 1GB ATI Radeon 5870HD. Most of the time, the GPU/memory clock speeds of the card operate at three levels: 157Mhz/300Mhz when idle, 400Mhz/900Mhz when playing a video or another 2D application, and 800Mhz/1200Mhz when under full load.

However, every so often, my card will become "stuck" at these maximum values, even when idle. ATI Overdrive also says that my card is under full load, even though I'm not running any sort of graphically-intensive software. So far, the only solution I've found is to reboot.

Anyone have any ideas?

The driver version is 8.831.2.0. I guess updating to the most recent driver is probably a good first step, so I'll do that.