I've had 2 580exii's mess up using the new PW's. Did the same thing yours is doing, a full power pre flash, and no flash during the exposure. I bet if you set it to manual at 1/1 and test fire it, then to 1/128 and test fire it you'll see no difference in the power of the light. Its full power any time it fires no matter the setting. I got 1 fixed about a month ago at CFSC in Newport News, Va. It was out of warranty, so repair and shipping cost me $120 and some change. Repair sheet said they replaced the battery box. 2 weeks later, my other 580exii did the same thing. Both of them messed up while using HSS. It seems I didn't have a problem until I started using them outside and the flash would have to go into high sync mode.