[Solved] Duplicate entry '17900' for key 'PRIMARY' (Errno: 1062)

Just had this when trying to approve a guests post, any ideas as to what problem could be?

An error was encountered

The error occurred on line 1539 in /home/.../extensions/pun_approval/functions.php

Database reported: Duplicate entry '17900' for key 'PRIMARY' (Errno: 1062).

When I go and look in phpmyadmin I see

first_post_id   17900
last_post_id  17900

It's a guest creating a topic....

EDIT:

I see now that the topic is already approved once and live in the forum, but there's still a topic to approve in pun_approval....
Is it possible this is bug when guest posts a new topic and the topic is approved?

EDIT 2: No, tested it again and working. Maybe the database was playing up or something. Solved.