Unable to call functions defined in XML2 contrib

Hi All,
 I am running PostgreSQL 8.4 offered with OpenSUSE 11.2. It works exceptionally well. I have installed the contrib package in order to use the functions provided by XML2/pg_xml as explained in this page: http://www.postgresql.org/docs/8.4/static/xml2.html
 However, when I try to run this SQL command: 
SELECT * FROM

      xpath_table('id','xml','test',                 '/doc/@num|/doc/line/@num|/doc/line/a|/doc/line/b|/doc/line/c',                 'true')     AS t(id int4, doc_num varchar(10), line_num varchar(10), val1 int4, val2 int4, val3 int4)   WHERE id = 1 ORDER BY doc_num, line_num

It returns an error saying that: 

 ERROR:  function xpath_table(unknown, unknown, unknown, unknown, unknown) does not exist
LINE 2:       xpath_table('id','xml','test',
              ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

********** Error **********

ERROR: function xpath_table(unknown, unknown, unknown, unknown, unknown) does not exist
SQL state: 42883
Hint: No function matches the given name and argument types. You might need to add explicit type casts.
Character: 21

Don't know what is wrong.
I am anxiously waiting for your reply.
 Franclin.