Digital Noise Issues - Clock Source Issues?

[Gorbies]

Hello,

I am running my UA LA-610 mic pre into an Apogee Rosetta which I am then connecting to my 003 Factory using the S/DIF ports. Also, I am running a Focusrite Octopre Platinum into my 003 by using the optical imports. I also have a LaCie external drive connected directly to my Mac via USB.

I have set the Clock Source in the Protools Hardware Menu to Optical but I am still getting digital noise, similar to the noise one gets if the clock source is not set correctly, only the noise I am getting is not quite as frequent.

By searching this forum, I discovered that one cannot run both Firewire ports at the same time because they create noise, which is why my LaCie is connected via USB.

Can anyone offer any insight as to why I am getting these pops and clicks?

It would be much appreciated.