MySQL error in file: /engine/modules/show.full.php at line 1024

Error Number: 3685

The Error returned was:
Illegal argument to a regular expression.

SQL query:

SELECT id, date, short_story, xfields, title, category, alt_name FROM dle_post WHERE category regexp '[[:<:]](23|24|26|27|24)[[:>:]]' AND MATCH (title, short_story, full_story, xfields) AGAINST ('Flipboard 2.0 — весь мир на страницах журнала По материалам: www.iguides.ru') AND id != 1005 AND approve=1 LIMIT 6