CoCreateInstance hangs - possible reasons?

Hello there,

Under certain circumstances, a CoCreateInstance call hangs my application. As it seems after some other parts of my program uses COM interfaces and such. I am trying to instanciate an object like this:

      HRESULT hresult;
      CLSID clsid;
      
      // initialize COM
      hresult = CoInitialize(NULL);

      // get component CLSID
        if (SUCCEEDED(hresult))
           hresult = CLSIDFromProgID(OLESTR("mydll.CMyComClass"), &clsid);
      
      // the class we defined in dll
      mydll::_CMyComClass *t;
      
      // create a class instance
      if (SUCCEEDED(hresult))
         hresult = CoCreateInstance(clsid, NULL, CLSCTX_INPROC_SERVER,
            __uuidof(mydll::_CMyComClass), (LPVOID *) &t);

      [ ... ]

Before other COM calls have been made, this code works perfectly. Afterwards, the CoCreateInstance() call hangs my application each and every time. It never comes back. No error message, it's just that nothing happens.

Any ideas? Urgent!