FB Connect: (417) Expectation failed

I developed a simple ASP.NET app, it was working fine, but now I can't get user info; I am getting this message:

The remote server returned an error: (417) Expectation failed.

and here's the code I'm using:

Dim FBUser As Facebook.Schema.user = Nothing
Dim connectSession As Facebook.Session.ConnectSession
Dim FBApi As Api

connectSession = New Facebook.Session.ConnectSession(ConfigurationManager.AppSettings("AppKey"), ConfigurationManager.AppSettings("AppSecret"))

If connectSession.IsConnected() Then
    FBApi = New Api(connectSession)
    Try
        FBUser = FBApi.Users.GetInfo()
        '' do some work
    Catch ex As Exception
      开发者_StackOverflow  FBUser = Nothing
        '' other work
    End Try
End If

This is really confusing, because it was just working fine for 2 weeks now !!

Thanks

I'm sorry for posting the solution that late, but it turned out to be some ISP related stuff. Adding this line to web config will help:

  <system.net>
    <settings>
      <servicePointManager expect100Continue="false"/>
    </settings>
  </system.net>

Or it equivalent by code.