Hmmm..... at the moment i have also these stuttering errors, i suggest it is related to the nvidia drivers.
Former i used an en8800gtx graphic card from asus, with a driver version 29x.xx and i was able to play ro2 without any errors. Sadly the graphic card crashed and i must buy a new one.
I bought a graphic card with the gtx570 chip and installed the latest nvidia drivers and since that i have the stuttering error.
At the first time ro2 was nearly unplayable for me, after i did some research i recognized that nvidia delivers an extra sound device with this card, so i disabled the nvidia hd audio driver in the device manager tab and doing the registry change, after that i was able to play the game but the stuttering error is still there.