AJAX site not operating the same in StateServer as InProc

Did you check with a test page(Without Ajax) that NLB is properly configured.

The NLB hosts tens of other web sites successfully.

Some of which i coded.
This is the first AJAX we publishing on the production environment and I'm pretty convinced is a session issue.

Can you pls post the exact exception you are getting?

Type : System.NullReferenceException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Message : Object reference not set to an instance of an object.
Source : App_Web_moj5dvjs
Help link :
Data : System.Collections.ListDictionaryInternal
TargetSite : Void ShowHideButtons(ElementSections, ButtonActions)
Stack Trace : at SourceManagement.ShowHideButtons(ElementSections section, ButtonActions action)
at SourceManagement.btnMainOfficeEdit_Click(Object sender, ImageClickEventArgs e)
at System.Web.UI.WebControls.ImageButton.OnClick(ImageClickEventArgs e)
at System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument)
at System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

The only thing that happens in that code is reading session variables.