Windows key hook suddenly stops working in DX11 game

I am creating a DX11 game and am using a low-level windows key hook to capture Alt+Enter so that I can toggle fullscreen using my own methods instead of having Windows do it automatically, which inevitably causes problems. A description of this process and details are available in the linked question. My problem is that the key hook consistently stops working after the 6th Alt+Enter for some reason. I am not unregistering it myself.

Here is the key hook code:

LRESULT _stdcall MyClass::WindowsKeyHook( s32 nCode, WPARAM wParam, LPARAM lParam ) {

	printf("Key hook called, nCode: %d. ", nCode);

if( nCode < 0 || nCode != HC_ACTION )  { // do not process message

		return CallNextHookEx( MyClassVar.GetWindowsKeyHook(), nCode, wParam, lParam );

}

printf(" Key hook status ok.\n");



	BOOL bEatKeystroke = FALSE;

	KBDLLHOOKSTRUCT* p = ( KBDLLHOOKSTRUCT* )lParam;

	switch( wParam ) {

//NOTE: Alt seems to be a system key when it is PRESSED, but a regular key when it is released...

case WM_SYSKEYDOWN:

if(p->vkCode == VK_MENU || p->vkCode == VK_LMENU || p->vkCode == VK_RMENU) {

MyClassVar.SetAltPressed(TRUE);

}

if(MyClassVar.IsAltPressed() && p->vkCode == VK_RETURN) {

bEatKeystroke = TRUE;

MyClassVar.SetAltEnterUsed(TRUE);

printf("Alt+Enter used.\n");

}

break;

case WM_SYSKEYUP:

//NOTE: releasing alt+enter causes a SYSKEYUP message with code 0x13: PAUSE key...

break;

		case WM_KEYDOWN:

break;

		case WM_KEYUP: {

if(p->vkCode == VK_MENU || p->vkCode == VK_LMENU || p->vkCode == VK_RMENU) {

MyClassVar.SetAltPressed(FALSE);

}

bEatKeystroke = ( !MyClassVar.IsShortcutKeysAllowed() &&

								( p->vkCode == VK_LWIN || p->vkCode == VK_RWIN ) );

			break;

		}

	}



	if( bEatKeystroke ) {

		return 1;

}

	else {

		return CallNextHookEx( MyClassVar.GetWindowsKeyHook(), nCode, wParam, lParam );

}

}

If you need more information, just tell me what is needed. I have no idea why this is happening, so I'm not sure what kind of information I need to provide. The only way to get rid of a key hook besides unregistering it explicitly is if Windows times it out, as far as I know. All MyClassVar methods are inline to be as fast as possible, and Alt+Enter is handled from a separate thread.

This question is also posted on http://stackoverflow...ok-stop-working