Powerbook: Audio feedback after sleep?

after the Powerbook has been asleep, and then awakened the microphone and loudspeakers cause a audio feedback
Niels S. Eliasen wrote on :

Hi guys I have this problem that after the Powerbook has been asleep, and then awakened the microphone and loudspeakers cause a audio feedback..... It is most irritating, as I then cannot use iChat....

any ideas ?