When listening to a remote stream over a poor connection, the SB will sometimes pause for a few seconds while it's "rebuffering". Pressing the power button during this period apparently works correctly - the SB goes back to the "off" screensaver (the clock, in my case). However, apparently when rebuffering has completed, the unit switches itself back on and resumes playing.

This is a Squeezebox 2 running firmware 84 against SqueezeCenter 7.0 - 15939.