Simple graph (generated by Companion) crashes with segmentation fault on windows

I’ve installed GNU Radio from binaries on my Windows machine exactly as
described in
http://code.ettus.com/redmine/ettus/projects/uhd/wiki/GNURadio_Windows
guide. (I used specified versions except some packages which was not
available). After two days of hard fighting this dll hell, I was able to
run
simple graph from GNU Radio Companion, but… it crashes !

My graph:
http://gnuradio.4.n7.nabble.com/file/n44753/untitled.grc.png
Block causing crash: QT GUI Frequency Sink
Crash happens not always (approximately each 5-10 time I execute it). It
happens only at startup (before widget appears or after at least one
rendering).

I used gdb to extract some info
(http://gnuradio.org/redmine/projects/gnuradio/wiki/TutorialsDebugging#Tutorial-Using-gdb-with-Pythonic-GR-applications).
Here is output from top_block.py:

<< CRASHES HERE >>
Some info from attached gdb stopped at SIGSEGV:

#3 0x633a367c in
#7 0x63365853 in gnuradio-runtime!??1thread_group@thread@gr@@QAE@XZ ()
saved eip 0x5291f25
called by frame at 0x707fc38
Arglist at 0x707fc04, args:
Locals at 0x707fc04, Previous frame’s sp is 0x707fc0c
Saved registers:
ebp at 0x707fc04, eip at 0x707fc08

Generated minidump: python.exe.4912.zip
http://gnuradio.4.n7.nabble.com/file/n44753/python.exe.4912.zip
OS: Windows 7 x64 Pro
Processor: Intel Core i5-2500 CPU @ 3.30GHz
Software (of course, all of them x86/win32 versions):
GNU Radio 3.7.2 (pre-compiled binary from Ettus R.)
Python 2.7.3
numpy-1.6.2-win32-superpack-python2.7
pygtk-all-in-one-2.24.2
PyQt-Py2.7-x86-gpl-4.9.6-1 (without extra options such as Qt runtime)
PyQwt-5.2.1-py2.7-x32-pyqt4.9.6-numpy1.7.1


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