I have upgraded forum from version 7.4.2. to version 7.5.6. and evrytime new user register I got following error:

Code
Tue, Nov 30 2010 14:06:52 -0500
 Script: /home/www/forum/scripts/adduser.inc.php - Line: 687 
insert into ubbt_USER_PROFILE
(USER_ID,USER_FLOOD_CONTROL_OVERRIDE,USER_REAL_EMAIL,USER_TOTAL_POSTS,USER_TITLE,USER_TOTAL_PM,USER_TOPIC_VIEW_TYPE,USER_TOPICS_PER_PAGE,USER_ACCEPT_ADMIN_EMAILS)
values
('17552','-1','test@hotmail.com',0,'stranger',1,'flat','10','')
- Duplicate entry '17552' for key 1

the initial number 17552 usually increments by one and all is written correctly but user receives a message:
UBB Message
We encountered a problem. The reason reported was
Database error only visible to forum administrators
Please click back to return to the previous page.

It was working well for one or two days but since it begins I can not solve the problem.

Regards.