ReportBook not showing in ReportViewer

[Peter]

I hope I haven't missed a post, but somehow I can't get the reportbook (Q2-2010) working. I've got the following code:

srMTO.MTOwsSoapClient soaplink = new srMTO.MTOwsSoapClient();
dsCompleteQuestionnaire1 = soaplink.GetCompleteQuestionnaire( QuestionnaireId );
Telerik.Reporting.Report QuestionnaireReport = new reports.rap_CompleteQuestionnaire();
QuestionnaireReport.DataSource = dsCompleteQuestionnaire1;
QuestionnaireReport.DataMember = "CompleteQuestionnaire";
ReportBook QuestionnaireBook = new ReportBook();
//QuestionnaireBook.Reports.Add( new Rapporten.rap_CompleteQuestionnaire_Front() )
QuestionnaireBook.Reports.Add( QuestionnaireReport );
reportForm.SelectedReportBook = QuestionnaireBook;

(last two lines are in reality not commented)

and the other form (reportForm with the ReportViewer):

Telerik.Reporting.ReportBook report = SelectedReportBook;
this.reportViewer1.Report = report;
this.reportViewer1.RefreshReport();

I had it working for the QuestionnaireReport (the same way), but realized I needed a front page. So I needed the ReportBook. But the content is just not showing. Neither with just the QuestionnaireReport.

Any ideas what I'm doing wrong?

PS. I know that the DataMember of the report is obsolete, but attaching it to the objectdatasource this way is not working (for me).