[PyQt] [PyQt 4.5] Freezing for emit signal

[Alexandr N Zamaraev]

Os Windows Vista Home Ru + sp1
g++ (GCC) 3.4.5 (mingw-vista special r3)
Qt 4.5 (self build)
sip-4.8-snapshot-20090409 (self build)
PyQt-win-gpl-4.5-snapshot-20090412.zip (self build)

I was unable to allocate a minimum example. Here is pseudocode situations:
[code]
class A(object):

   signal = QtCore.pyqtSignal()

   def __init__(self):
     super(A, self).__init__()
     self.signal.connect(self._do)

   def f(self):
     self.signal.emit()

   def _do(self):
     print 'A Hi'

class B(QtGui.QWidget, A):

   def __init__(self):
     super(B, self).__init__()

def main():
   app = QtGui.QApplication(sys.argv)
   b = B()
   b.f()
   print 'Opa'

if __name__ == '__main__':
   main()
[/code]
In this example, connect works without problems, but _do is not called.
But in my program in such a situation, the application freezes and have 
to kill him.