Updating my comment. I may have a different issue. I can't get USB audio out of windows for anything. I haven't had much time to play lately so I chalked it up to user error when reassembling my computer desk but now I'm not so sure.
Things I've tried:
Two separate USB cables straight into PC.
Updating to 14.04
Reinstalled FAS drivers
Reinstalled USB Firmware
Restarting computer and Axe-FX.
Axe FX is availible and selected as my output device in windows. I just get zero sound out of it.
Check the USB input level in the I/O menu USB/AES page. Make sure USB 1/2 is at 0 dB. Also, make sure the volume is turned up in Windows and is not muted there.