FULLTEXT mysql query keeps hanging

I have the following query:

SELECT a.address1, a.address2, a.address3, a.address4, a.name, a.id id,
c.description, c.id category_id, c.name cat_name,
MATCH (keywords)AGAINST ('".$search_keywords." ".$search_city."' IN
BOOLEAN MODE) AS score

FROM (sites a left join site_keywords b on b.site_id = a.id) left join
site_categories c on a.site_cat_id = c.id

WHERE MATCH (keywords) AGAINST ('(".$search_keywords.")
+(".$search_city.")' IN BOOLEAN MODE) ORDER BY c.name ASC"

Could someone explain to me why it hangs?

i'm confused!

I tried it not in Boolean mode too and still no luck!