Zombie Process after using a Windows subclass callback - windows

Question

I'm using the SetWindowSubclass(...) method of the Windows API to kind of "hook" messages transmitted to a WinProc that is out of the scope of my application.
My application is made of a core and plugins in DLL.
I've implemented such a Subclass in one of my plugins DLL.
I set the Subclass like this:
class MyPlugin
{
private:
static HWND s_OgrehWnd;
UINT_PTR m_uIdSubclass; //The ID of the Subclass WinProc
DWORD_PTR m_pdwRefData;
//....
public:
void MyPlugin::init();
LRESULT CALLBACK MyPlugin::windowProcSubclass(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData);
void MyPlugin::shutdown();
//....
};
//Set the subclass
void MyPlugin::init()
{
//...
bool resultsc = SetWindowSubclass(
s_hWnd,
MultitouchPlugin::windowProcSubclass,
m_uIdSubclass,
m_pdwRefData
);
//...
}
//The subclass
LRESULT CALLBACK MyPlugin::windowProcSubclass(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
switch(message)
{
case WM_GESTURE:
return MultitouchPlugin::g_cGestureEngine.WndProc(hWnd,wParam,lParam);
break;
}
return DefWindowProc(hWnd, message, wParam, lParam);
}
//Remove the subclass
void MyPlugin::shutdown()
{
//shutdown called - unregister stuff here
bool isSublcassed = GetWindowSubclass(s_hWnd, MultitouchPlugin::windowProcSubclass, m_uIdSubclass, &m_pdwRefData);
if(isSublcassed)
{
RemoveWindowSubclass(s_OgrehWnd, MultitouchPlugin::windowProcSubclass, m_uIdSubclass);
}
}
My problem is that when I quit the application, I can see the process that keeps running on in the 'Windows Task Manager' tool.
In debug mode, i've checked that it goes calls RemoveWindowSubclass(), and it does it.
If I remove my plugin with this code, there is no zombie process....
Does somebody has an idea about a solution to this problem?
Thanx in advance for the help