I've been haunted for a loooooooong time by sound drop-outs from captures from my vx2000 cameras.
I confirmed today that if i disable audio preview, Vegas captures it cleanly.
I'd tried to avoid this issue up til now by fresh defrags, and ensuring that i used the same camera for playback that recorded the tape.
It's been terrible to deal with.
So nice to have this answer, even if i don't understand the "why" of it!