Created ToolTip For Grid, It is working fine, same code ASP.Net 2.0 not working.

HI, I am working with ASP.net 1.1 , Created ToolTip For Grid, It is working fine, same code I copied to server which is ASP.Net 2.0 , It is Giving following error, How to Resolve? Please any one can help this? Server Error in '/RaviTest' Application. -------------------------------------------------------------------------------- Value cannot be null. Parameter name: key cannot be null or empty Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.ArgumentNullException: Value cannot be null. Parameter name: key cannot be null or empty Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [ArgumentNullException: Value cannot be null. Parameter name: key cannot be null or empty] System.Web.UI.ClientScriptManager.RegisterClientScriptBlock(Type type, String key, String script, Boolean addScriptTags) +1958607 System.Web.UI.Page.RegisterClientScriptBlock(String key, String script) +78 OptyWeb.VL_Plans.Page_Load(Object sender, EventArgs e) +645 System.Web.UI.Control.OnLoad(EventArgs e) +102 System.Web.UI.Control.LoadRecursive() +45 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +950 -------------------------------------------------------------------------------- Version Information: Microsoft .NET Framework Version:2.0.40903.27; ASP.NET Version:2.0.40903.27