I just purchased the Firehawk and a Fishman Loudbox Artist (I also play a nylon string acoustic). It's a great combination and the amp is small and portable yes powerful enough. Since the amp is designed to be extremely clean sounding, I find that it's a great combination with the firehawk.
I had the same issue. I was able to resolve it by:
1. Using a different computer
2. Using a different USB cable
3. Doing the 1.1 update before the 1.2 update
4. Re-trying a bunch of times
I'm not sure which of these helped, but I was glad it got resolved.