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user_id=1269908

Something changed on the computer I'm testing on, and the 
crash happens way less often (say 1/10 of the times in debug 
mode, and very rarely in Release mode).

The compiler is MSVC7.1 on WXP, using Python 241

This is the stack of the main thread

 	7ffe0304()	
 	ntdll.dll!77f5b5d4() 	
 	kernel32.dll!77e7a683() 	
 	msvcr71d.dll!_close_lk(int fh=0x00000003)  Line 115 + 
0x4a	C
 	msvcr71d.dll!_close(int fh=0x00000003)  Line 60 + 0x9	
C
 	msvcr71d.dll!_fclose_lk(_iobuf * str=0x1027c898)  Line 
127 + 0xc	C
 	msvcr71d.dll!fclose(_iobuf * stream=0x1027c898)  Line 
58 + 0x9	C
>	python24_d.dll!file_dealloc(PyFileObject * 
f=0x00919ec8)  Line 308 + 0xd	C
 	python24_d.dll!_Py_Dealloc(_object * op=0x00919ec8)  
Line 1870 + 0x7	C
 	python24_d.dll!frame_dealloc(_frame * f=0x00972960)  
Line 394 + 0x67	C
 	python24_d.dll!_Py_Dealloc(_object * op=0x00972960)  
Line 1870 + 0x7	C
 	python24_d.dll!PyThreadState_Clear(_ts * 
tstate=0x00892c88)  Line 200 + 0x6c	C
 	python24_d.dll!PyInterpreterState_Clear(_is * 
interp=0x00894f48)  Line 93 + 0x9	C
 	python24_d.dll!Py_Finalize()  Line 401 + 0x9	C
 	TestPyThreads.exe!main()  Line 33 + 0x8	C++
 	TestPyThreads.exe!mainCRTStartup()  Line 259 + 0x19	
C
 	kernel32.dll!77e8141a()

and this is the stack of the other thread (_threadstart)
(the crash is here, where "if (frame->f_exc_type != NULL) " 
gets called with frame == NULL)
>	python24_d.dll!reset_exc_info(_ts * tstate=0x00892c88)  
Line 2861 + 0x3	C
 	python24_d.dll!PyEval_EvalFrame(_frame * 
f=0x00972960)  Line 2490 + 0x9	C
 	python24_d.dll!PyEval_EvalCodeEx(PyCodeObject * 
co=0x00943ad0, _object * globals=0x008e3230, _object * 
locals=0x00000000, _object * * args=0x008c104c, int 
argcount=0x00000000, _object * * kws=0x00000000, int 
kwcount=0x00000000, _object * * defs=0x00000000, int 
defcount=0x00000000, _object * closure=0x00000000)  Line 
2730 + 0x9	C
 	python24_d.dll!function_call(_object * func=0x009431f0, 
_object * arg=0x008c1038, _object * kw=0x00000000)  Line 
553 + 0x40	C
 	python24_d.dll!PyObject_Call(_object * 
func=0x009431f0, _object * arg=0x008c1038, _object * 
kw=0x00000000)  Line 1751 + 0xf	C
 	python24_d.dll!PyEval_CallObjectWithKeywords(_object 
* func=0x009431f0, _object * arg=0x008c1038, _object * 
kw=0x00000000)  Line 3419 + 0x11	C
 	python24_d.dll!t_bootstrap(void * boot_raw=0x008c8148) 
 Line 433 + 0x1a	C
 	python24_d.dll!bootstrap(void * call=0x0012f694)  Line 
166 + 0x7	C
 	msvcr71d.dll!_threadstart(void * ptd=0x009101a0)  Line 
196 + 0xd	C
 	kernel32.dll!77e7d28e()

as you can see, the crash is also happening at a different 
place than what I had observed before, but I cannot find the 
stack that I had in that case.