I've noticed my cards do that from time to time. Also I've noticed they fluctuate PPD up and down on the same WU. I haven't paid too much attention to it.
You don't have any VGA -> DVI adapters? I'd have thought you have a mountain of those in a closet somewhere. Those are the best for the dummy plug as you can just slide the resistors into the VGA input on the adapter.
“If you don't dip your words in sugar, rainbows and teddy bears people will think you wish to hunt them down to torture and eventually kill them.” -DanTheBanjoman