I've the same problem than you.
i got the same error message when running mkinitrd (no module raid0 found for kernel 2.6.9).
i've posted a new thread in redhat category, the title is : mkinitrd failed with message "no module raid0 found for kernel 2.6.9"
I got some answer there asking me to install modutils and compile the kernel with all the raid options. I havn't done any of that yet (just read this answer few minutes ago).
i've also found a thread on another forum with same kind of problem:
I've tried to apply the patch provided but it gave me an error...
Hope someone can help us.