Canon has admitted a malfunction that occurs with Firmware Version 2.0.3, in which the manual recording levels for C1/C2/C3 are changed and the camera becomes unable to record audio if the power is turned off (or if Auto power off takes effect) after registering “Sound Recording: Manual” in the camera user settings.
For customers who have already updated to the new firmware, when using the camera with the mode dial set to C1/C2/C3, set the sound recording settings to Auto.
Firmware Version 2.0.3 incorporates five enhancements to the movie function and a fix to the manual sensor cleaning function of the EOS 5D Mark II camera.
Download firmware upgrade at: Canon