You have to find a release of dahdi-kmdl which matches your kernel or you have to upgrade your kernel to one that you can find a match for.
You have to completely remove the old asterisk ("yum delete zaptel" should remove the lot).
Now install the new Asterisk and dahdi rpms.
Now upgrade sail to one of the 2.4 releases (2.2 won'run with dahdi)
Done.
Kind Regards
S
.