There is an issue with Bing and Brutile 0.7.3 that is used in RC2 that have been fixed in 0.7.4 that will be used in 1.0 final...
A temporary workaround could be to use
string userAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:220.127.116.11) Gecko/20080404 Firefox/18.104.22.168";
string referer = "http://www.bing.com/maps/";
ITileSource tileSource = new TileSource(new WebTileProvider(new BruTile..Web.BingRequest(BruTile.Web.BingRequest.UrlBing, token, BruTile.Web.BingMapType.Roads), userAgent, referer, false), new SphericalMercatorInvertedWorldSchema());
Please note that this will not
work with brutile 0.7.4, since it's working now due to the Bing-bug in 0.7.3...
Or you could just upgrade to Brutile 0.7.4, that will solve your problem