"Input string was not in a correct format" on use stored procedure

Hi.

I got a problem with stored procedure in LightSpeed.
The store procedure and procedure's entity and is generated automatically on lightspeed model.
if I run application,
it's throwing me an "Input string was not in a correct format" error. ...

Durring debuging it's throwing me a information: about "null" in datatype procedure parameters, but
datatypes are declared right...

What I should to do ?
Is there any solution ?

greets

Could you provide us with a stack trace please?  Thanks!

Thank You for answer.

Here is a stack trace code:

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +7469351
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +119
   System.String.System.IConvertible.ToInt32(IFormatProvider provider) +46
   System.Convert.ToInt32(Object value, IFormatProvider provider) +31
   ..(IDataReader ) +55
   ..(TypeModel , QueryExpression , Order , String , Boolean , Boolean ) +217
   ..(TypeModel , QueryExpression , Order , String , Boolean , Boolean ) +77
   ..(TypeModel , IList , String , Boolean ) +104
   ..(TypeModel , ProcedureQuery , IList ) +220
   ..(UnitOfWork , TypeModel , ProcedureQuery , IList ) +80
   ..(TypeModel , ProcedureQuery , IList ) +52
   ..(ProcedureQuery , IList ) +79
   Mindscape.LightSpeed.UnitOfWork.Find(ProcedureQuery query) +220
   Panel_Atrakcje.BazaDanych.AtrakcjeUnitOfWork.GetEventsPage(Int32 startRowIndex, Int32 maximumRows) in c:\projects\byway_asp_trunc\manager\bazadanych\lightspeedmodel.cs:1903
   Panel_Atrakcje.Wydarzenia.listaWydarzen.GV_ListaWydarzen_DataReLoad() in c:\projects\byway_asp_trunc\manager\Wydarzenia\listaWydarzen.aspx.cs:193
   Panel_Atrakcje.Wydarzenia.listaWydarzen.Page_Load(Object sender, EventArgs e) in c:\projects\byway_asp_trunc\manager\Wydarzenia\listaWydarzen.aspx.cs:45
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627