An error with voice transmission

hi all

i’m using two USRP and two daughterboards RFX2400

and want to send voice( built in GNU radio examples)

after i write commmand (./rx_voice.py --f 2400M) in receiver terminal
then write (./tx_voice.py --f 2400M)in

transmitter terminal the following error apear :

Exception in thread Thread-1:
Traceback (most recent call last):
File “threading.py”, line 460, in __bootstrap
self.run()
File
“/usr/local/lib/python2.5/site-packages/gnuradio/blks2impl/pkt.py”, line
164, in run
self.callback(ok, payload)
File “./rx_voice.py”, line 88, in rx_callback
fg.audio_tx.msgq().insert_tail(gr.message_from_string(payload))
NameError: global name ‘fg’ is not defined

can some on helps me

thanks

Mohamed