Xtend + Arduino Mega - Serial problems

Hi. I´ve made my Xtend modules talk to each other using X-CTU terminal. But for some reason i cannot communicate my arduino mega serial port with xtend. I´ve already test the serial port from arduino and it´s working perfect, but trying to use with xtend or it didnt work or just send strange characters like dots and uncomplete words. I´ve set the RF power to 10mw and 100mw because i´m using indoor and 6m from one antenna to the other. Also set the RF and Serial to 9600bps.
Can any one help me?
Using two Arduinos Mega and two Xtend-900-SI