I just thought I would share for others' reference... AJA Tech Support just helped me solve a problem where our MacPro with Leopard running AJA Kona LHe version 5.0 drivers was outputting jerky and lagged video (both thru analog and SDI outputs) while video in the Canvas window was smooth.
There is an Expansion Slot Utility for the MacPro located in System/Library/CoreServices/
This allows the bandwidth allocated to each PCI slot to be configured. It was set to the default, which is the first option - x16 Lane Graphics Slot + One x8 and Two x1 Lane Slots. In my situation, it needed to be set to 'x16 Lane Graphics Slot + Two x4 Lane and One x1 Lane Slot' in order to give enough bandwidth to the Kona card (in Slot 3).