Hi, I am using matplotlib in a pyqt application, in which I am displaying an image on a FigureCanvas. My installation is Ubuntu 10.04-64bit. This has been working like a charm for several months but recently my application has started crashing with the following trace: File "/usr/lib/pymodules/python2.6/matplotlib/backends/backend_qt4agg.py", line 83, in paintEvent FigureCanvasAgg.draw(self) File "/usr/lib/pymodules/python2.6/matplotlib/backends/backend_agg.py", line 314, in draw self.figure.draw(self.renderer) File "/usr/lib/pymodules/python2.6/matplotlib/artist.py", line 46, in draw_wrapper draw(artist, renderer, *kl) File "/usr/lib/pymodules/python2.6/matplotlib/figure.py", line 773, in draw for a in self.axes: a.draw(renderer) File "/usr/lib/pymodules/python2.6/matplotlib/artist.py", line 46, in draw_wrapper draw(artist, renderer, *kl) File "/usr/lib/pymodules/python2.6/matplotlib/axes.py", line 1701, in draw im.draw(renderer) File "/usr/lib/pymodules/python2.6/matplotlib/artist.py", line 46, in draw_wrapper draw(artist, renderer, *kl) File "/usr/lib/pymodules/python2.6/matplotlib/image.py", line 237, in draw im = self.make_image(renderer.get_image_magnification()) File "/usr/lib/pymodules/python2.6/matplotlib/image.py", line 182, in make_image x = self.to_rgba(self._A, self._alpha) File "/usr/lib/pymodules/python2.6/matplotlib/cm.py", line 166, in to_rgba x = self.norm(x) File "/usr/lib/pymodules/python2.6/matplotlib/colors.py", line 763, in __call__ elif vmin==vmax: File "/usr/lib/python2.6/dist-packages/numpy/ma/core.py", line 3119, in __eq__ check._mask = mask AttributeError: 'numpy.bool_' object has no attribute '_mask' Strangely the bug seems to be intermittent, i.e. rebooting seems to temporarily fix the issue, but it always returns. Is this a known issue? Could I somehow fix this by reverting some of the Ubuntu packages to older versions? Thanks. Patrick