I have following method having following line inside it
HtmlPage.Window.Invoke("showPopUp",new string[] {"Hello from Silverlight"});
I have one htmlhost inside the page which contains script as
function showPopUp(msg){
alert(msg);
}
Whenever Invoke is getting called it throws exception saying Failed to invoke : showPopUp
Try to put your
showPopUpfunction into the .aspx page or set .html page as start page.