I've got an Apogee Duet firewire interface running into my G4 mac. I'm using the program Reaper.

In reaper I can choose whether to use the duet as my output or the built in audio/my speakers computer headphone jack as output.

In the past I used a blue snowball usb mic and when sending recorded audio from reaper to the speakers had no problem, now if I send audio recorded with the duet to the built in outputs it seriously messes with the data, I've been getting clicks and clacks and also drops in speed/pitch. weird stuff. This does not happen if I choose output through the DUET in reaper, and playback using that as output. THings sound fine. Only when sending to the computer output.

I've checked the sound preferences on the computer and everything is normal there, any other audio sounds fine.
using an AKG 414 xII if that changes anything at all, which I'm sure it doesn't

thanks to anyone who can lead me in some kind of direction!