A problem with node system

When I require "?q=node/add/xxx", the error follows appears on top of the page:
user error: DB Error: unknown error
query: SELECT n.*, u.uid, u.name, u.data FROM node n INNER JOIN users u ON 
u.uid = n.uid WHERE n.nid = 'xxx' in database.pear.inc
Any xxx course this error, e.g. blog, image, poll....
I am using drupal 4.4.2 with PostgreSQL 7.4 and php4 on FreeBSD 5.2.1 with 
apache2

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