vBulletin3 Db and Prefix

I am having a problem with the vBulletin3 Db and Prefix field...

I enter the database name in the field but amember is giving me following error message:

vBulletin3 Db and Prefix - incorrect value. Error: Table 'trade_amember.trade_forumsuser' doesn't exist

I am using a different database for vbulletin than amember, but the user has full access to both databases.

My vbulletin config file shows as follows:

// ****** DATABASE NAME ******
// This is the name of the database where your vBulletin will be located.
// This must be created by your webhost.
$config['Database']['dbname'] = 'trade_forums';

// ****** TABLE PREFIX ******
// Prefix that your vBulletin tables have in the database.
$config['Database']['tableprefix'] = '';


Is there something I am missing?

PLEASE HELP!