Input string was not in a correct format when you click on a Reports menu item in CRM 4.0

You created a custom view for reports and when you click on this item, Grid throws an error saying input string was not in correct format. You turn on the tracing and find the stack trace as below:

   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   at Microsoft.Crm.Application.Controls.ReportsGridUIProvider.RenderRow
   at Microsoft.Crm.Application.Controls.AppGridUIProvider.Render
   at Microsoft.Crm.Application.Components.UI.DataGrid.RenderData
   at Microsoft.Crm.Application.Components.UI.DataGrid.RenderInnerHtml
   at Microsoft.Crm.Application.Components.UI.DataGrid.get_InnerHtml()
   at Microsoft.Crm.Application.WebServices.AppGridWebService.Reset

I bumped into the same error and after much research found that this occurs because i did not had report type as one of my columns. Any reports grid need to have report type as a mandatory column. In order to fix this, follw these steps:

1. Log on to Microsoft Dynamics CRM as a System Administrator.
2. Click Settings and then click Customizations.
3. Click Customize Entities and open the Report entity.
4. Click Views and then open custom report.
5. Add the ReportTypeCode column to the custom report view.
6. Publish the Report entity.