The only time I had an err message was when fitting a lens with the camera turned on. I inadvertently brushed the shutter button part way through lens fittment and the err message appeared. I was going to take it back to the dealer and had already started to re-box it. Having left the battery out for nearly four days I re-fitted it just as a final check before embarassing myself in the shop and the err message had gone. I am not saying this is a panacea but it worked in this instance.