New MacBook Pro graphics card?
Yes this is normal. Both the 15" and the 17" MacBook Pro have two graphic cards and use the Intel HD graphics for normal function and switch to the ATI Radeon when a more graphically demanding application is being run. Also when you connect the external display the ATI card kicks in in order to drive both of your screens. This is why you get the blue screen flash when you connect and disconnect an external monitor (the graphics source is being switched)