Who's fault was it?

Because you where sharing the lane with other traffic (you where not following the cars, but riding along side them) it wouldn't surprise me if it was your fault as you where not really moving with the flow of traffic. You might want to do a little research into the laws for motorcycles in the same scenario (cutting traffic) to see what they have to say. Of course the standard IANAL disclaimer applies and Tony's point about the best lawyer winning is pretty valid as well.

-Mike