I have CS4 and I have a client who has given me the raw footage files uncompressed from a 4D camera shoot.
What's a 4D? The dimension after 3D, implying that the images were shot across time, in both the past and in the future?
Could you mean 5D, as in Canon 5D Mark II, a DSLR that shoots video? If it is a 5D, does the term "raw footage files uncompressed" mean that these are stills shot in Canon's RAW format? Or does this mean video?
Oh, it can't be video, because a 5D Mark II shoots highly-compressed video, but you say it's uncompressed.
I have a feeling I know what's wrong, but without accurate information it would be just a shot in the dark.
The obvious: Your client's monitor color settings ar hopelessly mis-tweaked? Or conversely, he is using specific color profiles and calibration and you are not? Whatever it is, it is certainly not a fundamental problem in AE. At best, it may require enabling the "Match legacy Quicktime Gamma" option in the footage interpretation, but that is pretty much all there is. Or to put it simply: If the footage looks okay in any media player on your (uncalibrated) monitor, then it is okay - the Gamma will be the same as Windows bog standard Gamma plus/minus any evil tweaking you have done on your monitor and graphics card and the absence of a calibration. And the differences in Gamma between Mac and PC would not generally be a problem, either, as Quicktime or any image viewer would already compensate by relying on the system's display library. Hence, we return to the point of your client's monitor claibration (or lack thereof) being the culprit here most likely.
Personally, I'm thinking in terms of two terms that just don't go together: AE 9 and H.264 video.