problems with the rtModel

[Wassim Soubra <Wassim.Soubra@sophia.inria.fr>]

Hello,
I am a new user of NS and I am trying to simulate
65 nodes with up and down links using the rtmodel
with a trace file but I get a long list of :
cannot open topo.trc
then another long list of:
insq: Cannot set event in the past
then finally:
can't read "nextEvent_": no such variable
    while executing
"lindex $nextEvent_ 1"
    (procedure "_o3467" line 4)
    (rtModel/Trace set-trace-events line 4)
    invoked from within
"$self set-trace-events"
    (procedure "_o3467" line 2)
    (rtModel/Trace set-first-event line 2)
    invoked from within
"$self set-first-event"
    (procedure "_o3467" line 10)
    (rtModel configure line 10)
    invoked from within
"$m configure"
    (procedure "_o3" line 6)
    (Simulator rtmodel-configure line 6)
    invoked from within
"$self rtmodel-configure                        "
    (procedure "_o3" line 4)
    (Simulator run line 4)
    invoked from within
"$ns run"
    (file "nodes.tcl" line 445)

is their a size limit for the trace file(mine contains
6626 lines)?

Thanks for any help
wassim