[ns] error while executing ns

hi,
the execution runs normally, NAM displays as it must but I'm getting the
following message on my terminal while executing app.tcl

xxx@xxxx:~$ ns app.tcl
num_nodes is set 8
INITIALIZE THE LIST xListHead
xxx@xxxx:~$ Missing required flag -x in: W -t 3.0

Missing required flag -y in: W -t 3.0

Parsing error in event.

and it doesn't stop until I type ctrl + c as if it waits for something

any ideas?

best regards
Leila