Try to search in http://rpm.pbone.net for "subversion-1.5" if that's what you need or just change it to "subversion-1.6" if in case you need that version limiting your search to "Centos 5" or "RHEL 5" and download the rpm that corresponds to your machine.
Install it via rpm as follows:
rpm -i subversion-package-name-here.rpm
If it says it conflicts with your existing subversion, check for the name of your existing subversion:
rpm -qa| grep subversion
and use the result for uninstalling the old package:
rpm -e subversion-old-package.bhabha
Then go back to installing the rpm as I detailed above.
Hope this helps,
Ismael Casimpan :)
