After upgrading our CentOS 5 box to the latest revisions last week (including Dovecot 1.1), we're seeing the following error message in the log files. Sieve was working fine with Dovecot 1.0.
I have yet to turn up anything via Google for this particular error. SELinux is not logging any error messages at the moment, so I'm pretty sure that we've properly allowed all the SELinux permissions.
# cat /var/vmail/dovecot-deliver.log
deliver(ruth@example.com): Jul 28 11:11:44 Error: dlopen(/usr/lib64/dovecot/lda/lib90_cmusieve_plugin.so) failed: /usr/lib64/dovecot/lda/lib90_cmusieve_plugin.so: undefined symbol: message_decoder_init deliver(ruth@example.com): Jul 28 11:11:44 Fatal: Couldn't load required plugins
# ls -l /usr/libexec/dovecot/sievec -rwxr-xr-x 1 root root 165152 Jun 11 03:21 /usr/libexec/dovecot/sievec
# ls -l /usr/lib64/dovecot/lda/lib90_cmusieve_plugin.so -rwxr-xr-x 1 root root 141328 Jun 11 03:21 /usr/lib64/dovecot/lda/lib90_cmusieve_plugin.so
# yum list | grep "dovecot" dovecot.x86_64 1:1.1.1-2_76.el5 installed dovecot-sieve.x86_64 1.1.5-8.el5 installed dovecot.x86_64 1:1.1.2-2_77.el5 atrpms
dovecot-devel.x86_64 1:1.1.2-2_77.el5 atrpms