Looks like the 2012 version of Crosspack adds an extra 1kb to the compiled arduino-usbserial.hex file. This causes the file to be too large, and overlap with the Arduino DFU Bootloader. Using the older 2010 version seems to solve this issue. Additionally, we found an easier “all in one” command for building the .hex file, and then loading it to the Arduino.
The updated info can be found here