http://web.canon.jp/imaging/eosd/firm-e/eosdigital4/firmware.html

 This firmware includes the following improvements and fixes:
  1. Fixes a phenomenon in which AEB (Auto Exposure Bracketing) shooting does not operate normally under these conditions.
When using AEB together with exposure compensation, the camera may fail to write the third shot to the SD card..
  1. Fixes a phenomenon in which the Live View exposure simulation warning indication does not properly display during Live View shooting.
Fixes a phenomenon in which the Live View exposure simulation warning indication, in which <Exp.SIM> would normally flash when the image is not being displayed at a suitable brightness level (under the conditions of low brightness and high brightness), does not display properly during Live View shootring..
  1. Fixes a phenomenon in which images cannot be played back after continuous shooting when a printer is connected to the camera or the video output terminal is used.