Copy DB from SQL Server 2008 to SQL Server 2012
DB Copy has a number of limitations as describe at: http://msdn.microsoft.com/en-us/library/ms188664.aspx

This includes not supporting the copying of System databases, Databases marked for replication, or any database not in a normal status.

However, it does support moving logins, jobs, and so forth.

The typically best way to copy a database with the fewest issues is to do a BACKUP from the source server and a RESTORE on the target server.  This is mentioned here in the discussion of strategies for copying databases:

http://msdn.microsoft.com/en-us/library/ms189624.aspx

If you also need to copy logins from the old to the new server, there are a couple of scripts documented at:  http://support.microsoft.com/kb/246133

SQL Agent Jobs can be scripted and recreated on the target server as well.