Duplicate entry ‘4’ for key 1 (database corruption(?))

‘lo

one of my users is getting this error with WordPress 1.5.2 – PHP 4.4.1 and mySQL 4.1.15 on FreeBSD/Apache 1.3.34

WordPress database error: [Duplicate entry ‘4’ for key 1]
INSERT INTO wp_posts (ID, post_author, post_date, post_date_gmt, post_content, post_title, post_excerpt, post_status, comment_status, ping_status, post_password, post_name, to_ping, post_modified, post_modified_gmt, post_parent, menu_order) VALUES (‘4’, ‘1’, ‘2005-11-07 08:30:19’, ‘2005-11-07 12:30:19’, ‘ddwdwdwdw’, ‘wdw’, ”, ‘publish’, ‘open’, ‘open’, ”, ‘wdw’, ”, ‘2005-11-07 08:30:19’, ‘2005-11-07 12:30:19’, ‘0’, ‘0’)

Warning: Cannot modify header information – headers already sent by (output started at /path/to/wp-includes/wp-db.php:98) in /path/to/wp-admin/post.php on line 170

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i’ve never encountered this issue before, even after installing/upgrading 100’s of WordPress installations. for some reason, new posts/pages are being assigned an ID “4” – using phpMyAdmin, i tried renaming the existing post with the ID “4” to “45”. when i tried posting a new entry/page, it worked but then an entry made after that renders the same error. tried changing themes, disabled plugins, it’s a no go. selecting the “Advance Editing” button also renders the same error.

the blog was originally WordPress version 1.2.x upgraded to 1.5 then 1.5.2 – not quite sure if that helps or is this simply nothing more than database corruption? please advise, thanks.