PostreSQL PostgreSQL 8.1.18 and Tsearch2 context error

Hi guys,

I'm working with full-text search on my project, however i'm receiving an
"Config file error: 7 ERROR: no tsearch config CONTEXT" message but i don't
know what it means.

The entire error message received is:

"SQLSTATE[F0000]: Config file error: 7 ERROR: no tsearch config CONTEXT: SQL
statement "SELECT doc_id, area_tem_id, headline(doc_nombre,
to_tsquery('spanish', 'prueba')) AS doc_nombre, headline(doc_autor,
to_tsquery('spanish', 'prueba')) AS doc_autor, doc_agno_publicacion,
headline(doc_descripcion, to_tsquery('spanish', 'prueba')) AS
doc_descripcion, doc_visitas, rank(doc_tsv, query) AS rank FROM
tbl_documento, to_tsquery('spanish', 'prueba') query WHERE query @@ doc_tsv
AND doc_activo='1' ORDER BY rank DESC, area_tem_id ASC" PL/pgSQL function
"buscardocs" line 26 at for over execute statement"

Can you help me about this error?, i will apreciate so much any suggestion
about it.

Thank's in advance,

Rodrigo