Forum major vbulletin 4.0.6. problem
 

This start happening today. I have upgraded to 4.0.6 5 days ago and everything worked fine. But today, when moderator answers to thread it is immediately closed after posting. They did not check the "close this thread after posting" or anything in moderation tools.
Nobody was messing with datebase or settings.
This does not happen every time, but frequently.

Please, does anyone knows what went wrong?