Azure AppfabricSDK 1.5 WebHttpSample not working with Proxy

by running the Sample "WebHttpSample" from AppfabricSDK 1.5 samples wit开发者_StackOverflowh Proxy (in my Company) I get the following exception:

The token provider was unable to provide a security token while accessing 'https://xxx-sb.accesscontrol.windows.net/WRAPv0.9/'. Token provider returned message: 'Die Verbindung mit dem Remoteserver kann nicht hergestellt werden.'.

in the app.config I add the proxy settings:

<defaultProxy enabled="true" useDefaultCredentials="true">

  <proxy usesystemdefault="True"/>

</defaultProxy>

The Connectivity Mode is Http. outbound TCP Connection is not possible. The same code works at home.

Can anybody help me? Thanks!!