I've had my SP-600 for several years, but I haven't used it since I got an SP-800. I thought I'd give the 800 a rest and put the 600 on my D300, and was surprised to see that the rear LCD of the SP-600 flashes continuously, whether on or off the camera, whatever mode I set it on and with several sets of different batteries!
I don't remember it doing this before. Can someone tell me if this is normal or not? This doesn't seem to affect the actual performance of the flash.