I recently purchased a Rebel XTi to replace my film Rebel. Will my Quantaray SLR film lens work with the digital? I have two one is a 28-80mm and the other is a 70-300mm. The reason that I ask is that with the 70-300mm, I get an ERR99 message and witt the 28-80 depending on the mode of operation as well as the shooting light sometime it works and sometime I get the ERR99 message. Any insight would be appreciated.