Arduino Uno + Adafruit Ultimate GPS Shield Serial issue
It looks like you are using the wrong baud rate somewhere.

You mentioned that you had checked your baud rates but check again because the second terminal window looked as if the baud rate was wrong. 

In your terminal window. Go to bottom right hand corner where it says 9600 and change it to match the serial speed set in your arduino code.

Or it could be that you are receiving too much data as per the bottom of this article:  https://learn.adafruit.com/adafruit-ultimate-gps-logger-shield/soft-serial-connect