Hi ever'buddy'

i need ur hand!!
i'm facing a big problem...
i'm recording in multitrack recording with Firepod + Cubase LE on Power book G4 Tiger Ram 2GB.
The problem is...for the begining of recording everything gone smooth and pretty!! but after a few minutes i got de noise...it appear when sound is recorded...disappear when no sound capture!!
u know wat i mean??
I wish buddies can give me a hand!!Wat's wrong with it??
is it bcoz of buffering setting??
anyone facing this problem??

Ray1018