SharePoint's User Profile Synchronization service is by FAR it's most complicated and painful part to deal with.  It is a bear to setup, modify, and maintain.  To add to that, if you are importing supplemental User Profile Properties from a BCS connection, like SQL, then you should know that importing URL and Person data types are not supported.

For example, if you have a SQL Table with a "Manager" field in it; you cannot import that field into the "Manager" Profile Property in SharePoint.  There is a very ugly and unsupported way of doing this <a href="http://social.msdn.microsoft.com/Forums/is/sharepoint2010general/thread/a64e997b-e6f4-4fcb-8551-2389f1edafd4">here</a>, but I would not recommend it.

<strong>The best solutions?</strong>
<p style="padding-left: 30px">
	1. Import these fields directly into AD from whatever connection your BCS connection is pulling from.  This is fairly simple when using Microsoft's AD API.<br />
	2. Create a Timer Job Definition that uses the BCS connection to get the Profile Properties from SQL and then use the SharePoint API to manually set the properties on each user's profile.<br />
</p>
Here's a really good post that explains <a href="http://blogs.msdn.com/b/spsocial/archive/2010/05/04/conceptual-view-of-how-user-profile-synchronization-works-in-sharepoint-2010.aspx">how the User Profile Synchronization service works</a>.