I may be able to help. I have a NCE 5 amp system and had a lot of problems at first. Obviously your computer and USB are OK if they worked on your friends system. I also could not get mine to work at first. I had two problems.
One Problem was a loose wire at the output from the base station to the programming track. The plastic wire connection unit plugs into the base station. Mine was loose and not making a good connection. If yours is also loose, it could explain why your computer and interface work on your friends layout and not on yours.
Second problem is that the sound decoders need more voltage. I finally got my system working with decoder pro, and it worked fine with non-sound decoders, but not with the Soundtrax and QSI units. Solution was to put more voltage to the programing track. I used a product called PowerPax. Worked great. I still have a few problems from time to time with QSI decoders, but everything else works just great with decoder pro.