Have you tried using some of the newer Catalyst 11.5 driver packs? They have a feature to force detection of TVs. Under Catalyst Control Center(CCC) on Desktop Management there is a setting called Advanced Display Settings.
There is a button that is called force TV detect, also Force Component Video, but only use Component if your using the Yellow RCA cable or it will cause issues ^.^
however you will need to use a monitor along with your tv in the inital setup or you will be unable to see what is going on. During the setup mark the TV as display 2 and when your ready to finish mark display 2 as Primary so your TV will be primary source and then you may unconnect the monitor . *TV should be marked as main monitor*