I just bought divinity 2 DKS from my local-ish gamestore. Installation went fine, at the launch of the game it asked for the serial. Type it in, no problem whatsoever.

Then I went to check if there are any patches. So I download the patch, install it then launch the game.

It asks for the serial again. Type it in, it doesn't accept it.
I double check for mistakes, but there are none. I tried to activate it manually and there it says that my serial is invalid.

I'm on win 7 64 bit.

I don't want to use iffy methods to get the game to work, so any help would be appriciated.