ArcGISTiledMapServiceLayer bl = new ArcGISTiledMapServiceLayer();
bl.Url = baseLayer; //this variable is just a string with the URL of the base layer map
bl.InitializationFailed += new EventHandler<EventArgs>(layer_InitializationFailed);
bl.Initialized += (a, b) =>
{
this.map1.Layers.Insert(0, bl);
};
bl.Initialize();
I've had this occur even if one minor code has an issue, that isn't necessarily reported as an error. Have you checked through all your other code?