AEB will also be canceled if you change lenses, replace the CF card, replace the battery, set a bulb exposure, have a flash-ready Speedlite, press the <CLEAR> button, or set the <> switch to <OFF>.
C.Fn C.Fn-9-1/3 prevents AEB from being canceled when you change lenses, replace the CF card, replace the battery, set a bulb exposure, have the flash ready to fire, press the <CLEAR> button, or set the <> switch to <OFF>