The issue can occur when you use a display with a refresh rate greater than 60Hz and results in significantly higher idle power consumption. Presumably, NVIDIA look into it and releae a driver update to resolve this.
While this "power bug" may sound like a minor issue, its effects are more insidious than one might expect. Using our trusty Watts Up power meter, I measured the idle power consumption of our testbed system at the wall. When the GTX 980 Ti is running at 135MHz as expected, that system draws between 80 and 90 watts at the wall. Kick up the refresh rate in a multi-monitor setup, though, and that figure jumps to between 130 and 150 watts. An affected PC running 24/7 is nearly doubling its idle power consumption, and that'll make for a hefty increase in one's power bill. Even weirder still, this problem doesn't seem to go away even if you turn off all of the monitors attached to the PC.