The digital download you get from registering your physical copy contains the exact same files as when you buy the digital version directly. If you have issues with your current installation of Dragon Age II, then you'll get the same issues if you buy the digital edition.
Instead, it's probably better to just try and solve this issue. When you downloaded and installed the game, did you make sure you uninstalled the game beforehand?
I would also like a few more details about your issue. Could you share the exact error message you're getting?