Getting this error pretty quick after starting: 

 

2V101/A IPS\convert\_Library::process: Out of range value for column 'member_posts' at row 1

That sounds like you've got a member account in vBulletin with a stored post count of more than 8,388,607 (the maximum our equivalent field can store). I'm fairly sure this would be a bogus value or a bug in vB that stored the wrong value. If you have a look at the users table in your vB database, have a look for any users where the 'posts' column is larger than 8388607 and adjust it to something smaller.

Yeah, I should've come back and replied to my own thread. Sorry. It was definitely that. 1,334,550,782 to be exact. The previous admins of the site I'm importing had fun with post counts and reputation counts........