Thank you for responding Ludek. I do not necessarily need or expect the report to remember my logon credentials but I would like an opportunity to provide them again, and have them submitted with the corresponding web service request. Similar to the behavior when connecting to an ODBC data source. When you open a report in the CR designer that utilizes an ODBC data source without a current connection to the database you are prompted to logon.
When this initial connection was defined, I was allowed to provide these logon credentials and they were submitted with the corresponding web service request. After closing the CR 2011 designer and reopening the report I can no longer reestablish a connection with the http xml url data sources used by the report because the web service requests are submitted without any logon credentials.
Thanks again for your assistance.