When you start the game up and the screen resolution adjusts itself press the ALT + Enter keys and see if switching to window mode has any effect.
If that fails edit the dragonage.ini config file should be at ~/Documents/BioWare/Dragon Age 2/Settings/ and try using 1920 x 1080 resolution initially and see if the game works then you can experiment on resolution settings
Can also try deleting the ini file in case a fresh one helps
Sadly, these did not work. I still have to use DirectX 9. Thanks though.
