Problem With M-audio Options

[tralli]

Hi everybody. My name is Helga Tralli and I´m 17 years old girl from Iceland. I´m running Tracktion on a Powerbook. I use a masterkeyboard and a Yamaha a5000 sampler along, midi connected to the Powerbook thru M-audio 1*1 Port (those blue small, plastic things). When I have sequenced a pattern and press play in Tracktion, it starts to play and everything seems Ok, but after a couple of seconds I start to noitce those cracky sounds (just like when you play something over 0db) and it sounds just like some midi error thing. Same for recording(midi recording ofcourse) but only more cracky-poppy-annoying sounds, sometimes when I´m doing sustain notes in recording those popup sounds break the sound and force the note I´m playing to stop. This is driving me crazy, does anybody know what to do?
Thanks in advance.

Helga Tralli.