I am booting BT4 from USB and all my hardware I have tested so far works just fine.

I was able to connect to my network on a separate card while using the Edimax in monitor mode.

I also stopped NetworkManager and networking and was still able to use the card in monitor mode once...

I have the same card and I think I might have found the solution. Try starting the NetworkManager script.

# /etc/init.d/NetworkManager start
# airmon-ng wlan0 start
# ifconfig mon0 down
#...