The AudioRecordSelector (System) seems not wo work properly under Windows Vista. Since in Vista the record source is no more selectable via the Mixer, but via the control Panel → Sound (by the way: additional settings for enabling the Stereo Mix as a source are necessary), VVVV seems not to find the option and offers just a (nil) at the Device Pin.
(Btw, only VVVV problem I found under Vista so far!)