[ns] error in tcl file

when i am trying to generate nam file it gives error : "Flow 1 starts at time 0.00 Segmentation fault (core dumped)" plz give me solution how to solve this problem mkc.tcl---

[ns] error in tcl file

sir, when i am trying to generate nam file it gives error : "Flow 1 starts at time 0.00 Segmentation fault (core dumped)" plz give me solution how to solve this problem thank you