Sorry guys but your Rawhide section doesn't list sudo. Sudo-1.5.9p1-2.src.rpm under Red Hat 6.0 Intel. If you have shadow and MD5 passwords enabled, sudo refuses all password entries. Turning off MD5 passwords and converting passowrd to crypt style permits sudo to work. I don't think this is /etc/pam.d/sudo configuration problem as adding md5 to the password entry doesn't fix it (it shouldn't anyway). This could be a problem with the implementation of PAM calls in sudo or a problem with PAM itself.
The sudo shipped in Powertools 6.0 should work.