Canon MARK II EOS 5D Instruction Manual page 207

The movie shooting quits by itself.
If the card's writing speed is slow, movie shooting may stop
automatically. Use a card with a read/write speed of at least 8 MB per
sec. To find out the card's read/write speed, see the card
manufacturer's Web site.
If the movie file size reaches 4 GB or if the movie is shot for 29 min. 59
sec., the movie shooting will stop automatically.
When the movie is played, camera operation noise can be heard.
If you operate the camera's dial or lens during movie shooting, the
operation noise will also be recorded. Use an external microphone
(commercially available) (p.123).
Display & Operation Problems
The LCD monitor does not display a clear image.
If dust is adhering to the LCD monitor, wipe its surface with a lens cloth
or soft cloth.
In low or high temperatures, the LCD monitor display may seem slow
or might look black. It will return to normal at room temperature.
Few tabs and options are displayed on the menu screen.
In the fully-automatic modes (1/C), some tabs and options are not
displayed. Set the shooting mode to d/s/f/a/F (p.40).
Part of the image blinks in black.
The [4 Highlight alert] option is set to [Enable] (p.129).
A red box is displayed on the image.
The [4 AF point disp.] option is set to [Enable] (p.129).
Troubleshooting Guide
207