Notice the top of the database error:
Code:
Database error in vBulletin 3.8.6:
It still thinks you are running 3.8.6 like it was never upgraded to 4.0.5. Did you run the upgrade script finally to completion? The database error where it talks about the postid column is an old pre-4.x column which was dropped in 4.0. So, if your files are 4.x files, then that error is caused by a modification.