We've run across this a few times, the Beta emulator likes to have a date time from July. Often times this doesn't matter but if your doing anything like oAuth where they time is validated with the server to be within a certain range it will reject the request. Came across this forum post that was helpful to explain how to delete the emulator state and get a real current date - http://social.msdn.microsoft.com/Forums/en-US/windowsphone7series/thread/70cefc55-e345-4448-b0df-edfadcd6f884
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