Just thought I'd share this useful mysql query by Wayne Luke that I found on vbulletin.com that finds duplicate posts within each thread. You can then easily delete those dupes.
http://www.vbulletin.com/forum/showthread.php?t=285501
If you've ever had 2 instances of the NNTP importer running on the same newsgroups by mistake, you'll really benefit from this. But it works just as well finding dupe posts inadvertently posted by your own vb users or from Usenet users.
The first time I ran it yesterday, I found thousands of dupe messages that have built up over the years connecting to Usenet. Now that they are all cleaned out, I'm going to run it on an regular basis before each build of our sitemaps.
I hope that you find it useful in conjunction with this mod. -- Rik