It looks like the changes for bug #5000 Changin EditMode in Script wrecks memory break the python interpreter. Since this is critical, I have #ifdef'ed those out of BPY_interface.c and Window.c. Did not touch Armature.c. The ifdefs are tagged with /* bug 5000 */ This means bug #5000 is back in play. Interesting to note that according to #5846, only scripts run from the script menu and not via Alt-P were broken.