I've had that problem over and over. We have three different EOS bodies and the Canon lenses all work fine as well as the newer off brand but there are a few off brand lenses we have that will not work with some of the bodies yet will work fine on the others. Seems a quirk in the programmimg and the bodies don't seem to be able to talk to the lens. I don't let it worry me too much, we don't use the 35mms too much any more, just on "lightweight" safaris and such.