9.2 won't load C-language function

I have a C-language function I've been using on 8.4 for a long time. On
9.2 it won't load:

test=# set search_path = public;
SET
test=# 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":
libopenbabel.so.4: cannot open shared object file: No such file or directory

But libopenbabel.so.4 does exist:

# ls -l /usr/local/pgsql/lib/libopenbabel.so.4
-rwxr-xr-x 1 root root 18250709 2012-10-09 18:05
/usr/local/pgsql/lib/libopenbabel.so.4*

There seems to be some difference in the library search path from 8.4 to
9.2. For administrative simplicity, I don't use ldconfig, besides which it
wasn't needed for 8.4.

What changed in how libraries are loaded between 8.4 and 9.2?

Thanks,
Craig