nam exec problem-help

[Pang Kun <pk@atm.mdc.tsinghua.edu.cn>]

Hi, everyone,
When I tried to exec "ns ../ex/simple.tcl". it displayed

210
0.00374999999999999
running nam...
nam: unknown event at offset 21 in 'out.nam'
nam: 'V -t * -v 1.0b6 -a  0

Who had met with this problem?  BTW, I installed ns-allinone under Redhat5.1.And all the validation were done
successfully.
Help pls.