Pressing volume up and down at the same time on the Desire HD Does anyone know what holding the volume button on both up an down does on the Desire HD?

I occasionally do it by accident and the phone vibrates, then about 10 seconds later vibrates again. During that 10 sec the phone is noticeably slower... But what, if anything, else does it do?

I'm running CyanogenMod 7 RC4
Since the volume buttons are actually one button in a kind of rocker configuration, I don't think pressing both at once is supposed to do anything.  I.e. if the button was built properly you wouldn't be able to press both at once, but it's not built properly and you can indeed press both sides at once, at which point the phone seems to go "Eh?".

I get various results, including one of the buttons being ignored, both being ignored, and some weird vibration effects (one long vibration or a couple of pulses).

It doesn't feel right to me, so I try not to do it...