Cannot ApplyLogOnInfo on a table in a Read-Only RPTR Report

I'm using a Crystal Report Viewer in my .Net app and i use the following code to relocate tables in my 'normal' RPT reports:

           With crConnectioninfo

                .ServerName = <<DSN Name>>

                .DatabaseName = <<Database Name>>

                .UserID = <<ODBC User ID>>

                .Password = <<ODBC User Password>>

            End With

            crRpt.Load(<<Full path to Crystal Report>>)

            crTables = crRpt.Database.Tables

            Dim crTable As CrystalDecisions.CrystalReports.Engine.Table

            For Each crTable In crTables

                crTableLogoninfo = crTable.LogOnInfo

                crTableLogoninfo.ConnectionInfo = crConnectioninfo

                crTable.ApplyLogOnInfo(crTableLogoninfo)

            Next

              ReportViewerCR.ReportSource = crRpt

It all works perfectly when i use a 'Normal' Crystal report i.e. any RPT file

However, when i use a Read-Only Crystal Report, RPTR, the code fails at the line

crTable.ApplyLogOnInfo(crTableLogoninfo)

and i get the following error message:

"Illegal operation on Crystal Reports Read-Only (RPTR) report. Please check release notes to get more information"

Can anyone please help?

Many thanks,

Jan