I've had the old 580EX for years. Just picked up a 580EX II to try. Mounted it on the camera hotshoe and fired off a bunch of shots, and it worked fine. Then I was trying something else out yesterday. I had my camera in my Newton CR bracket with the Canon OC-E3 cord. On the cord hotshoe, I had my FlexTT5 mounted and my old 580EX on the FlexTT5's hotshoe. I'm able to fire just my 580EX or fire it in combination with a couple of strobes, triggered by the FlexTT5. Then I decide to swap the old 580EX for the 580EX II. It doesn't fire. I removed it and installed it again - nothing. I put the old 580EX back on there, and it works fine. I put the 580EX II directly on the camera hotshoe with nothing in between, and it works fine. Is there some connection problem between the 580EX II and the FlexTT5 hotshoe that I haven't heard about (I wouldn't have been paying attention since it wouldn't have been an issue for me until now)?

