We just got back from a wedding had a problem we've never had before. Many times I would shoot a series of shots and the flash went off only about half the time. We are using the Canon 580 EX II one is about a year old and the other was literally brand new. The batteries we used were energizer rechargeables. We thought that it was the recycle rate however we switched to advanced lithium (non-rechargeable) and it did the same thing. I am not sure what happened because I've shot fast before without this problem. However, I've never shot in cold (Florida?) weather before. Is it the recycle rate that is causing this issue? It started doing it during family shots inside the church. Then it got even worse when we took the bridal party outside (i couldn't feel my hands, it was so cold). and then in the reception hall. I switched out batteries and it would happen again so I'm not sure if it was the batteries or something else. Any ideas?