Just got a Speedlite 580 EX II and am having some issues with it on my Canon 50D. It worked fine for about the first 60-70 shots but now just gives me black pictures instead of nice flash illuminated ones.
The flash is set to ETTL and recognises/displays all the camera/lens parameters. If the camera is set to P or (box) it recognises that an external flash is attached and sets the shutter speed to 1/60 .. but the resultant picture is almost jet black with only a couple of highlights visible.
If I now set the camera to M with a shutter speed of 1/125 and f4.5 and the flash to M, I get a nice picture and well illuminated.
Does anyone have any ideas? I've gone through the manual and am at a loss as to what suddenly went wrong.