Canon Speedlite 540EZ TTL Flash "eos rebel xsi" Questions

...Rebel XTI and the speedlight wont work on it. The flash works on all my other cameras its just the new digital. The camera's hot shoe works with my studio strobes so I am guessing it isnt the camera. ...

...EOS Rebel XSi, al querer sacar el flash no se acciona y me envia un mensaje en la pantalla solicitandome Err 05 "Se obstruyo la salida del flash, Desconecte y conecte el interruptor de corriente". Ya ...