If you will be installing the SharePoint Server Public Beta on Microsoft Windows Server 2008 R2 or Microsoft Windows 7 you will need to download and install an update from http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=23806 to resolve an issue that occurs in Microsoft SharePoint Server 2010 when provisioning Service Applications or when accessing pages that make service calls. These operations will result in an error "System.Configuration.ConfigurationErrorsException: Unrecognized attribute ‘allowInsecureTransport’. Note that attribute names are case-sensitive. (C:Program FilesCommon FilesMicrosoft SharedWeb Server Extensions14WebClients<Service Area>client.config line <Line Number>)".
If you have already installed Microsoft SharePoint Server 2010 on a server running Microsoft Windows Server 2008 R2 or Microsoft Windows 7, Microsoft SharePoint Server 2010 does not need to be reinstalled when the update becomes available; however, Service Applications that have been successfully provisioned without the update installed may need to be removed and re-provisioned once the update has been successfully applied.
Bill Baer, Technical Product Manager – US-SharePoint