The Axis menu item to open the tool editor works when Axis is first started, but typically only once. I have not figured out what is required to cause the error, ie at what point the menu item begins to be ignored.
The bug has existed for quite a long time. Launching tooledit from the command-line still works, however.
it is possible that this problem is related to ticket 329, which seems to hint at a problem with internationalisation.