I thought it might be my previous install of postfix, dovecot, spamassassin, etc... so I simply re-installed the OS on the box, then installed ZCS and its been running solid for a week now w/o any issues.
FWIW - I did a clean install of CentOS 5x with bare minimum base. I then ran the ZCS install.sh script and installed the needed dependencies, all via yum. After that ZCS installed just fine. I think I had an issue with CentOS 64bit install. I don't recall offhand if I found a way around it or if I just used the 32bit version for this test. If only I kept better notes
