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 (./ --f 2400M) in receiver terminal
then write (./ --f 2400M)in

transmitter terminal the following error apear :

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

can some on helps me