Just days after releasing a firmware update that brought 24 fps video to the 5D Mark II, Canon has pulled the update due to a malfunction that occurred.
Photographers who used the new firmware discovered that in a certain situation, the firmware would cause the camera to be unable to record audio. After receiving reports of this issue over the past couple days, Canon has pulled the update from the firmware page and has put up a notice, saying:
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.
If you’re already using the new firmware, you can avoid this issue by having your sound recording settings set to “Auto” when using C1/C2/C3.
Canon is currently working on a new update that fixes the problem, but has not announced when it may be available.
Looks like they should have tested the firmware more before setting it loose.