G4 400 (704 Mb) + Delta 1010 + Dp4 = Poping Sound, I have a poping sound in all apps. Options

[Redrum]

Well, I have just purchased and installed MAC OS X (with all the upgrades that internet allowed me) and the Digital Performer 4, and also installed the Delta-1010 drivers to use my Delta 1010 Sound Card with OS X (Core Audio) and with Digital Performer 4, and I have set up the computer Sound System as "Multichannel Delta-1010" for in and out sound.
Since I did that, I tested how it sounded putting a CD in my computer and played a song, but suddenly, some pops and sound drops started to happen. I tried also a DVD, and a demo song from the Digital Performer 4, and the same problem happened. Then I thought it might be that I have choosen the wrong "Delta" configuration in the Sound System for the computer and I changed it to "Analog 1/2 Delta 1010" for soun in and out, and in the DELTA CONTROL PANEL I made some arrangements so only the Delta 1/2 in and out meters are all the way up in the MIXER INPUT and also I set up the PATCHBAY / ROUTER to "Monitor Mixer" in the Analog Out 1/2 as the manual recommended, but the problem is still there... it feels as if the Delta 1010 is not capable of handling the audio properly and it pops. What should I do? Thank you very much for your help.