FreeBSD 4.3, PHP 4.0.6 & unixODBC -- Undefined Symbol

I had previously attempted to get the Openlink ODBC drivers work with iodbc and PHP. I was having no luck and turned to easysoft's solution, which includes unixODBC. I re-configured PHP (removing the config.cache file) and used --with-unixODBC=path/to/unixODBC instead of --with-iodbc=/path/to/iodbc. However, when starting Apache, I now get a 'Cannot load /usr/local/libexec/apache/libphp4.so into server: /usr/local/src/lib/libiodbc.so.3: Undefined symbol "pthread_mutex_unlock"'. The version of Apache that is installed is 1.3.20. I must not understand something about unixODBC because I didn't think libiodbc should even be getting loaded. Regardless, does anyone have a fix? Thanks, Joe