[Dovecot] Multiple versions of Dovecot installed

I have had to rebuild my 64-bit CentOS 5 email server and after installing dovecot rpms (using yum) I seem to have multiple versions installed:

dovecot-1.1.20-1_98.el5 - from ATrpms repo dovecot-1.0.7-7.el5 - from CentOS repo dovecot-sieve-0.1.18-6.1.el5 - from ATrpms repo

I have tried to install just the ATrpms version but when I do "yum install dovecot" the CentOS one always gets pulled in as well. Is this normal, or does it indicate that something has gone wrong in the installation process?

I'm having an issue with Dovecot sieve because it can't find a sieve plugin in /usr/lib64/dovecot/lda/. However, there is one in /usr/lib/dovecot/lda/. Do I have some sort or 32-bit/64-bit mismatch?