[imp] Problem with Horde Mail and Postgresql

[Patricia Castañeda]

I have:
RedHat 8.0
Apache 2.0.40-8
PHP 4.2.2-8
Imp 3.1.1
Horde 2.0
Pear 4.1.0
Postgresql  7.2.2-1

I have this problem:

Ha ocurrido un error fatal: DB Error: connect failed
línea 102 de /var/www/html/horde/lib/Prefs/sql.php

This error appears very frecuently last time, but not to all users.
There are two postgres tables very big, but when I execute VACUUM don´t
happen nothing.
The names of this tables are: 16561 and 16566 (who is who?)

To start I executed the scripts on the db directory for that reason I
think that tables are horde_users and horde_prefs or horde_categories?

I need some help.

Thank for your attention,

Patricia Castañeda