Shibboleth Developers

Well, I'm trying to setup a test shib sp with the new RPMS at 
http://shibboleth.internet2.edu/downloads/SRPMS/

After I install Xerces 2.6.1 with no problems, I then try to install 
xml-security:
rpmbuild --rebuild xml-security-c-1.2.0-2.src.rpm

I get an error:
error: Failed build dependencies:
        xerces-c-devel >= 2.3 is needed by xml-security-c-1.2.0-2.i386

Weird, cause I just installed 2.6 which is > 2.3

I know the webpage with the RPMS says something about "To specify the 
look-aside package, etc" but I'm a bit of a novice at all this and I'm not 
sure what that means.

Anyone else run into this? I hope it's an easy fix.

I'm on RHEL AS4.

Thanks,
Greg