mysql db replace issue

I have 13000 articles and almost as many comments. I have had a gigantic fail with ADSENSE lately. Down 80%.
I thought to try and remove all naughty words to see if it matters. I have an unmanaged dedicated server.

Using DB Manager, ADMINER and even the MYSQL on WEBMIN at the server I use the following code in SQL EXECUTE:

UPDATE wp_posts SET post_content = REPLACE (post_content, 'shit', 'crap');

I am told the syntax is correct, the results show:
Query executed OK, 0 rows affected. (0.713 s)

Searching the site finds 95 instances before and after.
The server looked into it for me and found nothing wrong with the DB or the SYNTAX but that is as far as they would go.

Any help in the matter would be much appreciated. I also have 500 assholes to rid of! ??
Thanx
kicker
rackjite.com