Thread not detaching?

[Duane Clark]

I have an application that is hanging, apparently because a thread is
not detaching:

000a:Call kernel32.ExitThread(00000000) ret=4077907f
000a:Call ntdll.LdrShutdownThread() ret=40376278
000a:Call PE DLL (proc=0x40ea2024,module=0x40ea0000
L"midimap.drv",reason=THREAD_DETACH,res=(nil))
000a:Ret  PE DLL (proc=0x40ea2024,module=0x40ea0000
L"midimap.drv",reason=THREAD_DETACH,res=(nil)) retval=1
000a:Call PE DLL (proc=0x40d4a02c,module=0x40d40000
L"msacm.drv",reason=THREAD_DETACH,res=(nil))
000a:Ret  PE DLL (proc=0x40d4a02c,module=0x40d40000
L"msacm.drv",reason=THREAD_DETACH,res=(nil)) retval=1
000a:Call PE DLL (proc=0x40d1405c,module=0x40d10000
L"wineoss.drv",reason=THREAD_DETACH,res=(nil))
000a:Ret  PE DLL (proc=0x40d1405c,module=0x40d10000
L"wineoss.drv",reason=THREAD_DETACH,res=(nil)) retval=1
000a:Call PE DLL (proc=0x407dc1d8,module=0x407d0000
L"user32.dll",reason=THREAD_DETACH,res=(nil))
000a:Call ntdll.RtlAllocateHeap(401e0000,00000000,00000080) ret=4080a08c
000a:Ret  ntdll.RtlAllocateHeap() retval=4026cfd8 ret=4080a08c
err:ntdll:RtlpWaitForCriticalSection section 0x403f2580 "syslevel.c:
Win16Mutex" wait timed out in thread 000b, blocked by 000a, retrying (60
sec)
err:ntdll:RtlpWaitForCriticalSection section 0x408849c0
"../../windows/user.c: USER_SysLevel" wait timed out in thread 000a,
blocked by 000b, retrying (60 sec)

The place it is happening is in WIN_GetPtr(), in the call to 
USER_Lock(). It is getting to RtlpWaitForCriticalSection() and hanging 
forever:

000a:Call PE DLL (proc=0x407dc1d8,module=0x407d0000 
L"user32.dll",reason=THREAD_DETACH,res=(nil))
trace:ntdll:RtlEnterCriticalSection Here
trace:ntdll:RtlEnterCriticalSection finished SpinCount
trace:ntdll:RtlEnterCriticalSection done
trace:ntdll:RtlEnterCriticalSection Here
trace:ntdll:RtlEnterCriticalSection finished SpinCount
trace:ntdll:RtlEnterCriticalSection done
trace:win:WIN_DestroyThreadWindows Destroying windows
000a:Call ntdll.RtlAllocateHeap(401e0000,00000000,00000080) ret=4080a08c
trace:ntdll:RtlEnterCriticalSection Here
trace:ntdll:RtlEnterCriticalSection finished SpinCount
trace:ntdll:RtlEnterCriticalSection done
000a:Ret  ntdll.RtlAllocateHeap() retval=4026cff8 ret=4080a08c
trace:win:WIN_DestroyThreadWindows Start
trace:win:WIN_DestroyThreadWindows 0 : 0x10022
trace:win:WIN_IsCurrentThread here
trace:win:WIN_GetPtr here
trace:win:WIN_GetPtr 1
trace:syslevel:_EnterSysLevel (0x40885ae0, level 2): thread a count before 0
trace:ntdll:RtlEnterCriticalSection Here
trace:ntdll:RtlEnterCriticalSection finished SpinCount
trace:ntdll:RtlpWaitForCriticalSection Here
err:ntdll:RtlpWaitForCriticalSection section 0x403f2580 "syslevel.c: 
Win16Mutex" wait timed out in thread 000b, blocked by 000a, retrying (60 
sec)

Any clues on what should be happening here?