'error synchronizing audio to midi" trouble with MACBOOK

I cant get logic running smoothly, with only ultrabeat and a few plug ins opened the trouble starts with 'error synchronizing audio to midi"

I get pops and clicks and delays in the sound when i use logic, i also have the random shutdown problem and the cpu whine.

Ive already tried all solutions of this list
http://docs.info.apple.com/article.html?artnum=304113

I use an RME Fireface 400, but the trouble also occurs with the onboard soundcard.