UBB.threads PHP Forum Software Community Forums UBB.threads 7 Bug Reports SQL Error #: 1062

Running UBB.threads™ 7.3.1 fine for over a year. Suddenly yesterday, on posting we have been getting this error:

Script: /home/cluster1/data/h/s/a1332841/html/belize/scripts/addpost.inc.php
Line#: 479
SQL Error: Duplicate entry '167180' for key 1
SQL Error #: 1062
Query: INSERT INTO ubbt_POSTS (POST_PARENT_ID,TOPIC_ID,POST_IS_TOPIC,POST_POSTED_TIME,POST_POSTER_IP,
POST_SUBJECT,POST_BODY,POST_DEFAULT_BODY,POST_IS_APPROVED,POST_ICON,
POST_HAS_POLL,POST_HAS_FILE,POST_MARKUP_TYPE,USER_ID,POST_PARENT_USER_ID,
POST_ADD_SIGNATURE,POST_LAST_EDITED_TIME,POST_POSTER_NAME,POST_MD5) VALUES
( 0 , 22111 , 1 , 1260408711 , '200.32.196.61' , 'test' ,
'test' , 'test' , 1 , 'book.gif' , 0 , 0 , 'markup' , 24 , 0
, 1 , 0 , 'xxxx' , 'xxxxxxxxxxxxxxxxxxxxxxxxx' )

Can't seem to track down what the problem is or even where to start. I have xxxx'd out the username and MD5.

Any ideas? Thanks in advance.