8.3 to 8.4 - Can't load dynamic shared library

I'm migrating from Postgres 8.3.10 to 8.4.4, and also from Fedora 9 to Ubuntu 10.04.

On 8.3.10, I have a C extension that worked on 8.3, but now refuses to load on 8.4:

CREATE OR REPLACE FUNCTION chmoogle_session_id() RETURNS integer
AS '/usr/local/pgsql/lib/libchmoogle.so', 'chmoogle_session_id'
LANGUAGE 'C' VOLATILE;
ERROR:  could not load library "/usr/local/pgsql/lib/libchmoogle.so": /usr/local/pgsql/lib/libchmoogle.so: undefined
symbol:_ZN9OpenBabel4etabE 

So it finds the first shared library, libchmoogle.so.  But the symbol _ZN9OpenBabel4etabE is from a second library, the
OpenBabel(chemistry) shared library, which is also located in 

   /usr/local/pgsql/lib/libopenbabel.so

On the Postgres 8.3 system, I simply put libopenbabel.so into the /usr/local/pgsql/lib directory, and everything worked
well. On 8.4, I can't seem to get it to load libopenbabel.so.  Other programs that use this library have no trouble
findingit. 

What (if anything) has changed from 8.3 to 8.4 regarding how it finds and links dynamic libraries?  What else should I
lookfor?  I'm stumped on this one. 

Thanks,
Craig