I have this problem more than month. Please look at VIDEO
https://www.youtube.com/watch?v=dJ31EZwjjhk
I try everything already.
1. Clear our database into empty data. (drop all table)
2. Try upgrade from 5.1.6 to 5.1.8 (last ver.)
3. Delete all files in vbulletin and re-install in empty folder with right config.php
Note, It's happen in CHROME browser only. (Good in FF and Safari)
That's not enought. It's still bug.
Please, Help me!