[OddsAre]

10.6.? if click the Apple in the upper right and About This Mac, it will tell you the exact version.

What brand/model internal hard drive is your secondary drive? Is it 7200RPM? How many GB's is the capacity and how many GB's are available? When was the last time you cleaned off and reformatted it?

Have you tried to record onto one of the other 2 "non-System" drives to see if they worked any better?

Have you ever run with just 2GB of RAM, just to see if maybe you have a bad stick of RAM? That happened to me once and it kicked off error after error.. 2GB ran smoother than 6GB with the bad stick. I slowly rotated the sticks around until I found the combination that singled out the bad stick.