xbee not talking

Hi to All,
I have established Wireless simplex comm Mode( Between MCU(Arduino ATMEGA8)and PC)using XBEE Modems. Tested by sending a string from MCU.
Also i have tested, Programm is running on MCU (BY uploading a code for counter) and transmitting this by XBEE modem and received at another XBEE modem, enjoying it on TEMINAL( BY X-CTU).
Thanks for your Help & Guidance