imshow() not working in while loop

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I am trying to write an imshow command in a while loop which is part of a void thread but the debugger wont pick it up saying there is no instance of an overloaded function "imshow" in argument list.

void* Display(void* params) {
    Mat *pImg = (Mat*)params;
    namedWindow("video", WINDOW_AUTOSIZE);
    while (bDisplay)
    {
        imshow("Video", pImg);
        waitKey(100);
    }

that is the code for the void thread. Any ideas on why it wont allow me to put an imshow in?