Regexps -- too complex?

Running 7.0.2 on Alpha/RedHat 6.2 256MB RAM

In order to implement a fulltext search, I have a func that parses list
of words and creates a regexp query with things like [[:<:]]( word |
word | ... )[[:>:]]

That query then is passed to backend...

Now the strange thing:

gamenet=# SELECT id, title,publishdate,categoryid FROM articles WHERE translate(title,'abcdefghijklmnopqrstuvwxyzâèçìîíïòðûþõäöü','ABCDEFGHIJKLMNOPQRSTUVWXYZÂÈÇÌÎÍÏÒÐÛÞÕÄÖÜ') ~ '(BLACK|SERIOUS|SAM)[[:>:]]'::text ;
id | title | publishdate | categoryid
------+-------------------------------------------------+-------------+------------
600 | Serious Sam ceïâ pie pircçjiem | 2001-03-22 | 149
523 | Black & White gaidîðanas svçtki | 2001-03-19 | 155
241 | Lorgaine: The Black Standard - íeltu varoòeposs | 2001-02-27 | 155
707 | Lorgaine: The Black Standard beta versija | 2001-03-23 | 156
1484 | Black&White tomçr neesot spiegu programma | 2001-04-18 | 155
1490 | Black & White FAQ | 2001-04-18 | 160
1496 | Black & White "ïaunais" FAQ | 2001-04-18 | 160
1732 | Black & White - pârdotâkâ spçle ASV | 2001-04-24 | 155
(8 rows)

gamenet=# SELECT id, title,publishdate,categoryid FROM articles WHERE translate(title,'abcdefghijklmnopqrstuvwxyzâèçìîíïòðûþõäöü','ABCDEFGHIJKLMNOPQRSTUVWXYZÂÈÇÌÎÍÏÒÐÛÞÕÄÖÜ') ~ '(BLACK|SERIOUS|WHITE|SAM)[[:>:]]'::text ;
id | title | publishdate | categoryid
----+-------+-------------+------------
(0 rows)

It seems that if the regexp is too complex (more than 3 |-ed
elements) it doesnt return.

Any ideas?