error while running swan

Where is the location of the following error:

Starting Simulation…
ns: _o14 monitor 1:
(_o14 cmd line 1)
invoked from within
“_o14 cmd monitor 1”
invoked from within
“catch “$self cmd $args” ret”
invoked from within
“if [catch “$self cmd $args” ret] {
set cls [$self info class]
global errorInfo
set savedInfo $errorInfo
error “error when calling class $cls: $args” $…”
(procedure “_o14” line 2)
(SplitObject unknown line 2)
invoked from within
“_o14 monitor 1”