mysqldump and mediawiki

[Joshua Whopper]

Hi all,
I wrote a php script to backup my databases. It works with all batabases but wikidb which is the name of the DB i use for MediWiki.

The command is

root[~]# /usr/bin/mysqldump -u yyyyyy -pxxxxxxxxxxxxx -S /media/hdb1/zan/Gestione/mysql/mysql.sock wikidb >/media/ext3/Backup_MySql/Wikidb_20120521-164555.sql

but I get following error

mysqldump: Got error: 1146: Table 'wikidb.category' doesn't exist when using LOCK TABLES

The eviroment is:
MediaWiki 1.14.0
PHP 5.2.11 (apache2handler)
MySQL 5.1.56-log

and now some strange things
from command line the above command works correctly (its not a permissions problem since the same command but with other BD works)
running mysql inside a terminal I get that following tables are present wikidb
+-------------------+
| Tables_in_wikidb |
+-------------------+
| archive |
| category | <--------- the missing table is present
| categorylinks |
| externallinks |
......
......
| user_groups |
| user_newtalk |
| watchlist |
+-------------------+
38 rows in set (0.00 sec).

If I check wikidb tables from phpmyadmin I dont see the "category" table and there are 34 tables instead of 38.

Any idea?

Thank you in advance