Digital Audio Out Breaking Up

When I use the digital audio out on my macbook pro, the audio breaks up intermittently. I can't associate it with a particular application running, but it seems as if it is not getting enough cpu because it may pause for a second, play fine, or cut out constantly. It happens using iTunes or streaming audio from the Web using a flash player. Is there a way to set process priority? or see if something is conflicting with the process that is playing the audio? Does anyone else have this problem?

Thanks for your help!