Xbee working??

Hi all
i am using Xbee s2 & X-ctu Version
initially while reading its modem parameter and firmware from X-CTU software it was showing modem name and its function-set when i tried to change the function set, then onwords its not writing to xbee and reading from xbee
so that
i have tried to re-flash but its not responding for those commands which is mentioned in the below link

can anybody tell me where is the problem? or my xbee is damaged?

Have you tried the techniques mentioned in the FAQs under XBee 802.15.4?