Make sure this is set correctly in the cartlab-vb-integrate.php file:
Code:
$vb_usertable = "user"; # vb user table name
As well the proper tables are inserted here as well:
Code:
# other tables that need userid's
$vb_userfield="userfield";
$vb_usertextfield="usertextfield";
Sometimes there is a "vb_" in front of the table names.
All database calls selects and opens have a die() condition on them with appropiate errors if there are any problems connecting to the phpBB's database and X-Cart's database you should see an error upon registering.
Are you experiencing any errors at all or are users simply not being created in VB's user table?