I just upgraded my 5.0.16 to 5.0.18 on OpenSuSE 10.2.
Everything worked fine except I was not able to utilize MTA to send e-mails with SSL authentication.
After spending 3 hours I found that /opt/zimbra/postfix/libexec/master was linked against /opt/zimbra/cyrus-sasl-18.104.22.168z/lib/libsasl2.so.2 which is inorrect. Should be /opt/zimbra/cyrus-sasl-22.214.171.124z/lib/libsasl2.so.2.
The way to solve the problem which indicate itself as "warning: SASL authentication failure: cannot connect to saslauthd server: Permission denied" in /var/log/messages was to delete old cyrus-sasl-126.96.36.199z directory and to create link cyrus-sasl-188.8.131.52z => cyrus-sasl-184.108.40.206z