Vsync might help depending on your system. Though it also might cause more problems,such as input lag. I personally play with Vsync off because i dont experience much screen tearing.
As for the issue itself..aye its known,many people have experienced this problem. Im not sure if its something the devs are considering as an issue to be fixed though. It happens because the game constantly streams data into the game world to reduce area loading times and this in turn can choke up slower processors.
It results in a strange occurrence where the higher your FPS,the more stuttering you will notice due to the streaming. For me it was most noticeable in Flotsam Forest..while traversing that enviroment i was averaging 30-40fps but was experiencing constant stutters. Whereas in Flotsam itself,my FPS would drop as low as 20 in heavily crowded areas and i was experiencing no stutters at all. Funny..lol
As said,i would recommend you download Dxtory and give it a try. In my experience this solves the problem for nearly everyone experiencing it.
http://dxtory.com/v2-home-en.html Download and install it,dont touch anything else in the program..just go to the Advanced tab and at the very bottom you will see an option that says "Limit Video FPS *number*". Set it to a number that suits you. Personally my choke point was at any amount of frames above 30.
Minimise the program,and run the Witcher 2..you should see an FPS counter in the corner of your game screen,and if everything is working correctly the number wont go higher then 30.
Hopefully,this will then be problem solved. No more mini freezes or stutters. =)