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
Standardbeta versija       | 2001-03-23  |        1561484 | Black&White tomçr neesot spiegu programma   | 2001-04-18  |
      1551490 | Black & White FAQ                               | 2001-04-18  |        1601496 | Black & White
"ïaunais"FAQ                     | 2001-04-18  |        1601732 | 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?