In the meanwhile, Canon has pulled the update from its support site while it works on a new firmware version to patch things up, but aside from a promise of "soon," there's no way to tell when exactly the new file will hit the pipes."Recently we have discovered 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. We apologize very sincerely for the inconvenience, but we are going to stop making this firmware available for download. For customers who have already updated to the new firmware, when using the camera with the mode dial set to C1/C2/C3, please either set the sound recording settings to Auto."
[Thanks to everyone who sent this in]