I had the same issue on Windows. I tried numerous Windows machines and had the same issue as you. But once I got home and plugged into my linux box, I was s-off and unlocked within minutes. Try a Linux system instead of Windows. And make sure you are S-ON or firewater will not do anything.
On a stock 4.09.605.1 using Windows 7, I was able to use firewater by following the instructions on http://forum.xda-developers.com/show....php?t=2742127 . To address any problems that may arise, read the entire thread.