Error creating Blt Vector?

[Bob]

Hi,
I'm using a BLT Vector in a program I wrote and it was working fine
until tonight.  I made some changes in my code but nothing near where
I create the vector.  Now when I try to create a vector I get this
error on the console:

Exception TclError: 'invalid command name "::blt::vector"' in <bound
method Vector.__del__ of []> ignored

and this error in the pop up window:

Error: 1
TclError Exception in Tk callback
  Function: <bound method Top.canvasRClicked of <__main__.Top instance
at 0x00906998>> (type: <type 'instance method'>)
  Args: (<Tkinter.Event instance at 0x009D67C0>,)
  Event type: ButtonPress (type num: 4)
Traceback (innermost last):
  File "C:\Python22\lib\site-packages\Pmw\Pmw_0_8_5\lib\PmwBase.py",
line 1690, in __call__
    return apply(self.func, args)
  File "net.py", line 126, in canvasRClicked
    newArc = Arc( self.canvas, self.sim )
  File "net.py", line 479, in __init__
    self.history = Pmw.Blt.Vector()
  File "C:\Python22\Lib\site-packages\Pmw\Pmw_0_8_5\lib\PmwBlt.py",
line 99, in __init__
    self.tk.call(_vectorCommand, 'create', self._name)
TclError: invalid command name "::blt::vector"

================================================
  Event contents:
    char: ??
    delta: 3
    focus: 0
    height: 0
    keycode: 3
    keysym: ??
    keysym_num: 3
    num: 3
    send_event: 0
    serial: 128
    state: 8
    time: 1785684158
    type: 4
    widget: .10320848
    width: 0
    x: 274
    x_root: 410
    y: 194
    y_root: 426

Can anyone help?
Thanks,
-Bob