[ns] ns-2.28, nam doesn't work!

[Lion Bedroo]

Hi all,
I've installed ns-2.28 many many times but I've got the same problem which is the nam file doens't work and can't be open.

1- path in .bash file is correct even I am not sure about the .bash_profile and what it is main function
2-I've changed agent.h by changing NULL to 0 but it did't work
3-I've tried ./configure the nam-1.11 because of the change that I've made in (2) but still didn't work
4-I've tried makefile to nam-1..11 but still didn't work
5-from cygwin I went to the path of nam-1.11 and wrote $nam but still didn't work
6-I've brought nam.exe and put it inside nam-1.11 but still didn't work


would any boday has an idea which could help!

thanks in advance 

Regards
Lion