wp7 ad sdk doesnt load page always?

I'm experimenting with the microsoft ad sdk in testmode with xna. When clicking on the ad it opens the browser but it doesn't always load the page. The url input area will just contain a "enter web address" and the page will be white. Not sure what the problem could be as it lo开发者_StackOverflow中文版ads the correct page sometimes.

I haven't used the Ad SDK, but try using HttpUtility.UrlEncode on the URL instead of just passing it straight to the WebBrowserTask.