Okay try this.
Change your style, build a new one off the default vBulletin style.
Next set the new style as the only style users can choose. If its' the style thats' creating all these database issues, then changing it for good, should remove them.
I used to use the TF Theme for my vBulletin gaming site:
http://buypoe.com/forum. At the time, I thought it was a great theme. However, upon switching that theme, I noticed massive changes in loading time - for better.