[ns] Problem running nam version 1.10

[Carlton DAVIS]

I installed the ns-allinone-2.27 package which includes nam-1.10
on a FreeBSD machine. When I try to run nam,  a lot of info is output
which looks like tcl code , then I am returned to the command prompt.
The last 3 lines it output before it exits, reads:
     : version conflict for package "Tcl": have 8.4, need 8.3
             while executing
     "package require -exact Tcl 8.3"

Any idea how I can fix this please?

Thanks much and best regards,

-Carlton