This might be related to bug #21156, but I'm not sure.
1) ./autogen.sh --prefix=`pwd`/bld --enable-xevie=no; make; make install
2) From three different shells sitting in my at-spi2-core directory:
b) gcalctool --gtk-module=`pwd`/bld/lib/gtk-2.0/modules/libspiatk.so
c) PYTHONPATH=`pwd`/bld/lib/python2.4/site-packages accerciser
3) In accerciser, select the "Numeric 8" button of gcalctool -- it's in the first subpanel of the last panel in the hierarchy. Go to the "Interface Viewer" tab and open the "Action" section on the right hand side.
4) Highlight the "click" action and then press the "Perform action" button.
Upon completing step 4, the action will take effect in gcalctool (i.e., an '8' will be entered in the display), but accerciser will now hang. Note that gcalctool does not hang, so it appears as though maybe accerciser is waiting for a reply it never receives.
I have managed to reproduce the bug, although it seemed to be random. One click did work, while another caused Accerciser to hang.
Have tried the steps provided using HEAD versions of at-spi2-core at-spi2-atk and pyatspi2.
The steps no-longer lead to an error, accerciser does not hang and '8' is seen in gcalctool.
pyatspi - 35719e716e96a7f1ef5c86c
at-spi2-core - 3564bdd84f28ee50e0fd42069ca60d033fbd6
at-spi2-atk - 3f0f32b8b49f702c554c28fecbbf4ed