Thanks to Davegrow from the Samsung Transform Ultra forums for his post which helped me fix this issue. As an addendum, i noticed that there may be a way to check if Google Talk has properly authenticated, without it obviously telling you otherwise. This comes from my brand new installation of CM18.104.22.168, os it may hust be me imagining it. After installation (and several reflashes after som Titanium Restoration headaches) i noticed that the Wi-Fi AND Mobile Signal bars were grey to start with, then changed colour to green. When Google Talk kept saying that it could not authenticate these bars remained grey throughout and after the Setup Wizard. Once i fixed this problem, they went back to green and i could start using market again. Hope that helps some people.