I have x86_64 and cannot reproduce your problem. Even valgrind doesn't catch anything:
gjc@dark-tower:Desktop$ valgrind python -c "import goocanvas"
==7691== Memcheck, a memory error detector.
[...]
==7691== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 155 from 1)
I have x86_64 and cannot reproduce your problem. Even valgrind doesn't catch anything: tower:Desktop$ valgrind python -c "import goocanvas"
gjc@dark-
==7691== Memcheck, a memory error detector.
[...]
==7691== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 155 from 1)
Could you run with valgrind, like I did above?