Exporting to pdf from crystal reports stopped working

I have a piece of code that was working fine and is all of a sudden throwing the following error

{Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack.}

on this line -- rd.ExportToHttpResponse(ExportFormatType.PortableDocFormat, context.Response, false, string.Empty);

rd is a ReportDocument.

this code was working fine. I do not know why it is throwing this error now! please help I need this solved!

public void ProcessRequest(HttpContext context)
    {
        ReportDocument rd = new ReportDocument();
        try
        {
            string path = context.Server.MapPath(ResolveUrl(GetReportPath()));
            rd.Load(path);
 
            if (GetIsODBC() == true)
            {
                string user = System.Configuration.ConfigurationManager.AppSettings["ReportUserName"];
                string password = System.Configuration.ConfigurationManager.AppSettings["ReportUserPassword"];
                rd.SetDatabaseLogon(user, password);
            }
            this.SetReportDataSources(context, rd); //set the data sources
 
            context.Response.Clear();
            rd.ExportToHttpResponse(ExportFormatType.PortableDocFormat, context.Response, false, string.Empty);
 
            context.Response.ContentType = "application/pdf";
            context.Response.Flush();
            context.Response.Close();
        }
        catch (Exception e)
        {
            context.Response.Clear();
            context.Response.Write(e.ToString());
            context.Response.Flush();
            context.Response.Close();
        }
        finally
        {
            rd.Close();
        }
    }

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