The current OLAP code has been tested successfully with XML/A connections to SQL Server 2000,5,8 Analysis Server. With respect to Mondrian, we have found that we have had issues with different versions. Internally we use JPivot code for OLAP communications, and at the time of development we used the most stable version available, but this was still fairly old at the time. At the time, this would work with SQL Server and some versions of Mondrian, but I am guessing you are using a much later version of Mondrian. What version of Mondrian are you using? I will attempt to replicate the environment here.