I too have had this problem but I don't know of any work-arounds. The problem is however not consistent on my machine and generally I run Lightwave and Carrara at the same time but having a dual processor system, I set the affinity to run each on separate processors until I begin rendering which I will go ahead and affinate both processors to software that I am rendering my end product on. With this in mind, having run Carrara alone and with other programs running in the background such as Poser and Lightwave, I have come to the conclusion that it is something more or other than a system error and more of a software bug based on certain system configurations, however that is my personal educated guess.