And part of the options as feeds IN are, as I read it:
"ambix3™ Technology - safety of investment with analog/digital interfaces (DVI-I, DVI-D, VGA) with up to 3 inputs simultaneously" - What IN are you using?
What feed are you taking OUT from the card to the Monitor?
I'm asking these 2 questions because presently I am having a major issue with a feed to an ExtMon which echo your issue to a tee! Vegas Hangs; need to kill in Task Manager; intermittent.
What setting do your have RAM Preview on? You could try adjusting this downwards.
I am starting to become more aware & conscious as to just how much or little I need to make Vegas work, with all the other Preview management features that 8 and 9 has brought. And how these features maybe demanding RAM and having RAM Preview set too high could impinge on the flow, and subsequently OUT to a monitor and this, in turn, affecting the core activities of Vegas?
I have no way or expertise in confirming or denying this.