Hmm....that is very odd. I have a odd question for you - are you using a third party battery grip?
Hmm....that is very odd. I have a odd question for you - are you using a third party battery grip?
5D is a pretty old body. How shiny looking are the contacts for the pins on the flash? Would not surprise me in the least if the issue was solved with a Q-tip and some alcohol to remove oil and dirt buildup. I can't remember if the plating on the 5D was gold or not but it is never a good idea to use anything abrasive on any of the electrical contacts when cleaning. Just remember that there should only be enough alcohol on the Q-tip to barely moisten it so that you can't have any run off to places it ought not to go.
Using genuine canon grip, did a wedding yesterday and no problems. Very weird, have checked contacts and cleaned them.
Also, why the hell are the 580ex ii external battery connection so weak! Used a flash battery pack and when connecting it the socket got pushed in the flash unit! Happened on both my 580s. Have done a DIY repair on it and seems to work. /end side note!