enthought/pyface — comment on commit 7955400dd123afb43fc444a422de9788f7a26082
File: pyface/ui/qt4/action/action_item.py line 137
By jdmarch:

Happens with this app wherever tested: Win7 with PySide 1.0.8 and 9, OSX 10.6.8 with PySide 1.0.9.

_qt4_on_destroyed is not called in the simple Tasks example in pyface.

In the attractors example in envisage, _Tool._qt4_on_destroyed is called, does have the same signature mismatch, but it is fine (no crash) after the signature-only change:

def _qt4_on_destroyed(self, control=None):
self.control = None

So our Tasks app may be doing some over-zealous or mis-timed object disposal.
This suggests that for now the signatures of both _qt4_on_destroyed's should be adjusted and that we should fix our app. I'll email you the OSX stack dump in case something strikes you.