When using jtds, Microsoft JDBC driver or JDBC-ODBC bridge to use MS SQL server
with Persistence API, the following error occurs 

RAR5111 : Error casting to javax.sql.Datasource :{0}

RAR5114 : Error allocating connection : [Error in allocating a connection.
Cause: com.microsoft.sqlserver.jdbc.SQLServerDriver]

Workaround (provided by Andrei Badea):
- undeploy the application from the server
- in the admin console (http://localhost:4848) make sure the connection
pool and the data source you created have been removed (remove them if
necessary).
- under the Server Resources node in the Project view open the
connection pool properties (right-click and Properties). Enter
"net.sourceforge.jtds.jdbcx.JtdsDataSource" in the DataSource Classname
field. Then open the Properties list (last item) and add the following
properties: serverName, portNumber and databaseName (their meaning
should be clear). Leave the other three properties there.

Expected fix: use appropriate DataSet classes for JDBC drivers