R – Crystal Report Bound to a Type Dataset Throws error when add column from related table

I am using Crystal Reports 2008 to design reports and the Crystal Reports 2008 runtime to execute them in a web application. I have created a simple typed DataSet and that has two tables TestTable1 and TestTable2. Each has a few columns like Id, Text1, and Text2. I created a test report which uses this Typed DataSet as it's DataSource. If I add the columns from just one of the tables TestTable1 or TestTable2 the report is easily executed with this code.

        report = new ReportDocument();
        report.Load(Server.MapPath("bin/testreport.rpt"));

        var ds = GetData();

        report.SetDataSource(ds);

        CrystalReportViewer1.ReportSource = report;
        CrystalReportViewer1.RefreshReport();

The problem is that when I add a column from the other table I get this message.

"Error in File C:\Windows\TEMP\testreport {94AF2363-CA61-4944-B63E-C0E6E0391C9A}.rpt: The request could not be submitted for background processing."

If I only have columns from one table it works just fine, but adding any columns from the second table gives this error.

Any ideas? I tried both with and without relations in the DataSet. I also tried a untyped DataSet.