The Canon 5D Mark 3 requires Camera Raw 7.1 or higher.
CS4 is only compatible with Camera Raw up to 5.7
To open Raw 5D Mk 3 photos you'll have to either:
a) upgrade to CS6, or
b) join the Adobe Cloud and get CS6
Alternatively, you can download the free Adobe DNG converter
Convert all the Raw images to DNG then edit the DNGs in CS4.