I've googled and searched for the past hour and I can't find anyone with a similar issue to mine. So just a few days ago, my 430ex II decided that it would stop letting me go into the menu on my 40D and change flash settings. I'm now getting the error message "this menu cannot be displayed. Incompatible flash or flashes power is turned off." Now, I know I can't access and change all of it via the menu, but I'm curious as to why it now won't let me? Does anyone else have or had this issue? Would it be dirty connections? I don't think so, since it still fires the flash no problem.