Starting yesterday, at seemingly random intervals my CPU is being pushed to ~100% usage for 3-4 minutes at a time. After some exploration, I think I've pinned it down to a problem with a playback device. When the CPU is pegged, if I open Playback devices I can see a "Headphones" device reappearing and disappearing several times a second. When the problem temporarily stops I can pull up the device's properties, and it seems to correspond to a front panel jack which I never use (and nothing is currently plugged into it). Right-clicking "Headphones" and choosing Disable does not seem to have done anything to remedy the problem.
What else can I try to stop this from happening?