Cannot connect to other databases since upgrading

Since I upgraded to CB 1.4 I cannot execute a mysql_select_db() statement to select any database other than the database for the Joomla site.

This call does not return an error, it does not return at all and I am left with a blank screen

Code as simple as shown below will fail for any existing database unless 'xyz' is the Joomla database

<?
$con = mysql_connect("localhost",$username,$password);
mysql_select_db('xyz',$con);
mysql_close($con);
?>

Any thoughts?

Thanks,
Dom

I restored my system from a backup that uses an older version of CB and my database accesses started working again.

Anyone have any thoughts on this?

Thanks,
Dom