420EX not syncing??

I have a 420ex that just stopped syncing with the shutter all of a sudden (using on a 10D). The unit flashes, but I think it's only shooting it's pre-flash, or something... or the second flash comes too late, perhaps. The e-TTL is not working or synchronizing properly. Has anyone else had this problem??

-dave-

reset your custom functions and see if this helps. you getting a long recycle time between flashes?

i'll have to try resetting the functions, but no, it seems to do a low power fire, and is not slow at all

-dave

Do you have 2nd curtain sync turned on? Probably not because you'd see the 2nd flash.

Can you post a sample pic, with EXIF information embedded? Or beside the pic.

Other than that it's pretty odd.

Well, probably following the same mind-set, I turned on rear curtain synch.. and still don't see a second flash. This leads me to believe it's not firing the "real" flash at all, only the "pre" flash. Also, the green "exposure OK" light does not come on the 420ex after the shot.

-dave-

Update:

after fiddling and screwing around with this i've noticed a pattern...

if camera and flash are off, with the flash mounted on the camera, then powered up, flash will not synch.

if leaving the camera AND flash ON I remove the flash and remount it, it synchs perfectly and consistently.

so what's up with that??

-dave-