The zip file (SF32u4_boards-master.zip) provided by SparkFun (www.sparkfun.com) for their FioV3 board does not work with Arduino V1.5.5
I have fixed this (with the help of Lauszus) and made a new zip file available on
http://www.forward.com.au/pfod/ArduinoProgramming/FioV3/index.html
See the README.txt file for more details http://www.forward.com.au/pfod/ArduinoProgramming/FioV3/sparkfunFioV3_1.5.5_README.txt