That's a bit strange. Basically '25749' is a number that is automatically generated by MySQL as the post id for the post that is being inserted. The auto_increment property is supposed to take care of that. But, that error is saying that post id already exists. I don't think I've ever seen MySQL do that before.
First thing to do would be to find out the actual max post id in the posts table. So try this SQL command:
select max(POST_ID) from ubbt_POSTS
