Sounds like you were bitten by the dreaded "Pin-1" problem on your Fast Track.
It is quite simple to fix pin-1 problems on balanced inputs and outputs. It is nearly impossible to fix them yourself on single-ended ports, and sadly Firewire and USB fall into that category. Using local power can help if the device is designed well, it may not help if the designer disregarded the rules<G>!

No not pin 1, The issue is with USB only, they will scream with nothing plugged in. Worst was it also showed in the SPDIF. This only happens with certain computer MoBo USb connections and did not happen with my laptop. But the device was not great anyhow and had a list of issues so I gave it away and moved on. 

USB is just as susceptible to the Pin-1 problem as any other connection...
 
In fact you'd be amazed at just how badly one can muck up any interface!!

Ok I see what you mean now. Thanks for the clarification.