Just wanted to check and see if anyone else has had issues with their 600 rt zoom not responding? I push the zoom button, then select it, but turning the wheel does not bring up any zoom range number or increase or decrease the range. It just stays "---." I checked my custom functions and auto zoom is not selected. Zoom function works just fine on my other 600s. This is the same flash I just sent into canon to have the bulb replaced when it burnt out, so it may be that this particular 600 is just a dog. Any other ideas on what the cause could be, or should I just send it in?