new 3.8.1 installation - DB error on adding member
 

This is a clean installation, after which I impex'd into it from 2.0.x vb forum.
Upon testing adding new members, I get a DB error. I do not get an with the details of the error. And the new user does not get the activation email.

I can see the the user get created in the DB, sitting in 'awaiting confirmation' user group.

http://www.jannah.com/f/register.php?do=addmember

Where should I look to start trouble shooting this problem.
thanks.