@jm .... There is another thread about that problem. That particular problem was there in X1 as well, but less previlant. Whatever they changed in X2 has brought it to the forefront.
According to the other thread it was reported but Cakewalk can not reproduce it, just like all the other problems with the PC, so dont expect it to get fixed anytime soon.
The only reason I upgraded to X2 was because of the engine improvements and the 'hope' that included some help for the PC. Its clear now that nothing has changed, well, actually its worse now because so many people are here talking about it right out of the chute.
You will get the typical , check your vid card, drivers, sound card, OS, and I bet that happens before I even finish writing this post. Trust me ... I've replaced everything in my daw but the wiring and nothing fixes this. Its a problem with sonar. It has been from day 1 but they dont know how to fix it.