I believe people thinking a banking collapse in Greece is fuelling a rally is purely psychological. The price is being bid up simply on the idea that it should be bid up.
It's probably always psychological when something like this happens but it doesn't stop people speculating and trying to find a reason 'why' to pin it on. Happens everytinme the price moves. "Why's it going up", "why's it going down", and even "why's the price staying the same" and so and people always look to the news to for the reason when it probably doesn't have anything to do with anything but supply and demand and panic buying or selling.