I don't know if it does the same thing to you guys, but while you're previewing clips through Vegas' Explorer window (with auto-read on), if you click on the Preview audio slider to lower/raise it, does it cut the preview?
It has come up before in various forms - it has to do with how Vegas deals with "focus". Didn't someone just post about the ShuttlePro and something like this, instead of play they got clips inserted on the timeline?