Note that there is no nsIWindow to be returning a cast to here. nsresult nsWindow::QueryInterface(const nsIID& aIID, void** aInstancePtr) { if (NULL == aInstancePtr) { return NS_ERROR_NULL_POINTER; } static NS_DEFINE_IID(kCWindow, NS_WINDOW_CID); if (aIID.Equals(kCWindow)) { *aInstancePtr = (void*) ((nsWindow*)this); AddRef(); return NS_OK; } return nsWidget::QueryInterface(aIID,aInstancePtr); }

there was no need for a QueryInterface in this code, so i removed it. marking fixed.

code level fix, marking verified. (bruce, reopen if you disagree)