I did finally get it working, but I don't know exactly what did it. I scrapped the entire server installation (RHEL 5 64-bit), and reinstalled RHEL 5 32-bit. I downloaded the latest release of Funambol 8 and found the SourceForge repo with the latest version of the Zimbra connector (
Browse Funambol Zimbra Connector Files on SourceForge.net). After installing again, it worked and I can now see the Zimbra module in the Admin Tools interface.