"Invalid group condition" Error opening Report in ASP.net

I am trying to open a report in ASP.net. This report opens and runs fine using the Crystal Reports Program (Professional). It has two subreports that it uses. Main datasource for the report is a stored procedure (SQL Server). When I try to run it in my aspx page, I get the following error:

CrystalDecisions.CrystalReports.Engine.InvalidArgumentException: Error in File (filepath): Invalid group condition.

Here is the code I am using to load the report:

protected CrystalDecisions.Web.CrystalReportViewer crViewer;

// CODE

ReportDocument rd = new ReportDocument();
rd.Load(Server.MapPath(Global.REPORTS_DIRECTORY + fileName));
rd.SetDatabaseLogon(username,password,server,initialDB);      
// SET REPORT PARAMETERS
crViewer.ReportSource = rd;
crViewer.DataBind();

Any ideas what could be wrong (since it does run fine in the CR Program)?