Recording With Cracks And Pops, in Logic Pro Options

[camarao]

Hi

I've noticed this problem:

I have a Powerbook g4 15" OSX 10.4.4, a Lacie Firewire external disc, a Terratec Phase 24 firewire soundcard, an M-Audio Midisport 4x4 midi interface, a Clavia Nord Lead, a Waldorf Xtk, Yamaha Fs1r, Oberheim Matrix 1000 and an Yamaha 01V digital mixer. The digital out of the mixer is connected to the digital in of the soundcard. In Logic Pro 7.1, when I record the stereo out of the mixer thru the digital cable (spdif) into the soundcard I get cracks and pops. I'm always recording to the external disc (7200rpm). I've tried the Powerbook's hard disk and I get the same problem. Usually the recorded file sounds good at the beginning, but after some minutes it starts to have those cracks and glitches. And I'm sure they're recorded. It´s not a playback problem. I'm recording at 24bit 44100hz. I've tried recording second time and it had no cracks and pops !
Does Logic need to play all the song before it is recorded ? Do I have something wrong on my preferences ? Is this a bug ?

I've also noticed that when I use Kontakt 2 and I play a song for the first time, as soon as the song pointer reaches the Kontakt notes Logic stops with the following message: " CoreAudio System Overload.The audio engine was not able to process all required data in time.(-10011)". When I play the song the second time, Kontakt plays with no problems and the song doesn't stop. Is this related to the cracks and glitches problem in some way ?

What do you think ?

Thank you.

Alex