Why can't my After Effects import .MP4 XDCAM files ???

I've searched everywhere for this and couldn't find the solution to it.

Whenever I try to import a .MP4 file my After effects says "After Effects error: file 'xxx.mp4 cannot be imported - this 'xxx.mp4' file is damaged or unsupported"

....but I've edited with XDCAM .MP4 files before, they worked on CS4 and CS6, and they are the best quality in my perspective.
Anyone know the solution to this problem ? if you do then please give me an answer, Thanks!!

Computer Specs:

CPU: Core2Duo E6600 2.4Ghz
Graphics card: GT630 4GB
RAM: 4GB
OS: Windows 7 Ultimate

Thank you for your time!

-Fl