I have experienced this error message while in a photo shoot several times. I use tamron lenses and I will be shooting fine, when suddenly I get this "no communication with lens" message. My lens appears to be attached properly. Sometimes I will then get a "00" number that cannot be changed under my aperature setting. I usually have to turn the camera off and then hope it all resets itself. ANy thoughts on what could be causing these problems? (My firmware is up to date by the way). Thanks.