Canon EOS 5D Mark II Instruction Manual page 225

No images can be shot or recorded.
The card is not properly inserted (p.29).
If the card is full, replace the card or delete unnecessary images to
make room (p.29, 160).
If you try to focus in One-Shot AF mode while the focus confirmation
light <o> in the viewfinder blinks, a picture cannot be taken. Press the
shutter button halfway again to focus, or focus manually (p.35, 84).
The image is out of focus.
Set the lens focus mode switch to <AF> (p.31).
To prevent camera shake, hold the camera still and press the shutter
button gently (p.34, 35).
If the lens has an Image Stabilizer, set the IS switch to <1>.
The maximum burst during continuous shooting is lower.
Set [8C.Fn II -2: High ISO speed noise reduction] to one of the
following settings: [Standard/Low/Disable]. If it is set to [Strong], the
maximum burst will greatly decrease (p.195).
If you shoot a subject which has minute details (field of grass, etc.), the
file size will be larger and the maximum burst will be lower as
mentioned on page 55.
ISO 100 cannot be set.
If [8C.Fn II -3: Highlight tone priority] is set to [Enable], the
settable ISO speed range will be ISO 200 - 6400. When [Disable] is
set, you can set any ISO speed (p.196).
Troubleshooting Guide
225