no mods or anything.  I just did the basic installation, which has been working fine for a months.  Then I suddenly started getting the error.

None of the users can enter new posts.  I haven't upgraded or changed any settings recently. The error is:

File: /...../public/post.php
Line: 180

PunBB reported: Unable to create post

Database reported: Duplicate entry '0' for key 1 (Errno: 1062)

Info:


PunBB version
    PunBB 1.2.12 - Check for upgrade
    © Copyright 2002, 2003, 2004, 2005 Rickard Andersson
Server load
    Not available (1 users online)
Environment
    Operating system: Linux
    PHP: 5.2.9 - Show info
    Accelerator: N/A
Database
    MySQL 4.1.22-standard
    Rows: 669373
    Size: 34.05 MB