Running on dual core Windows XP. 

The function should draw a parabolicish shape for each click on launch. But if you click Launch over and over, very fast, you get bizarre crashes instead: Python.exe has encoutered a problem, yadda. tcl85.dll. It rarely takes many clicks.

Apologies for the coding style; this has been hacked down from a larger app.

In the console window:

Exception in thread Thread-5:
Traceback (most recent call last):
  File "C:\Python27\lib\threading.py", line 530, in __bootstrap_inner
    self.run()
  File "C:\Documents and Settings\mayos\Desktop\PMT2\MyProjects\TkinterCrash.py"
, line 47, in run
    self.app.arrival_122((self.target, y, z))
  File "C:\Documents and Settings\mayos\Desktop\PMT2\MyProjects\TkinterCrash.py"
, line 100, in arrival_122
    self.label.config(text= str(message[0])+ " " + str(message[1]))
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 1202, in configure
    return self._configure('configure', cnf, kw)
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 1193, in _configure
    self.tk.call(_flatten((self._w, cmd)) + self._options(cnf))
TclError: invalid command name "source C:/Python27/tcl/tk8.5/menu.tcl"

Exception in thread Thread-4:
Traceback (most recent call last):
  File "C:\Python27\lib\threading.py", line 530, in __bootstrap_inner
    self.run()
  File "C:\Documents and Settings\mayos\Desktop\PMT2\MyProjects\TkinterCrash.py"
, line 47, in run
    self.app.arrival_122((self.target, y, z))
  File "C:\Documents and Settings\mayos\Desktop\PMT2\MyProjects\TkinterCrash.py"
, line 125, in arrival_122
    self.graph.create_line(self.trackCoordinates[tn], new_yz)
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 2201, in create_line
    return self._create('line', args, kw)
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 2189, in _create
    *(args + self._options(cnf, kw))))
TclError: invalid command name "line"

Also saw:
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 2201, in create_line
    return self._create('line', args, kw)
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 2189, in _create
    *(args + self._options(cnf, kw))))
TclError: bad option "665.4400009999997": must be addtag, bbox, bind, canvasx, canvasy, cget, configure, coords, create, dchars, delete, dtag, find, focus, gettags, icursor, index, insert, itemcget, itemconfigure, lower, move, postscript, raise, scale, scan, select, type, xview, or yview