error while loadig the application page in SharePoint 2010

Hi All,

When Approver trying to open the application page, he is getting below error.
CUstom Error Message: "Error while loading the task information. Task might have been deleted or canceled".
In our environment When user upload the document with Approval Workflow a email was sent to Approver. Then Approver will approve the document from his pending requests(SPGrid).
Here TaskEditForm is application page which located /_layouts folder, recently no code changes have done in our environment. But suddenly we are facing this issue, before that application worked fine and Approvers able to open the page and able Approve/Reject the document. Do i need to check any services? restarting server?

I can not debug the code in our environment. Could any body help me to troubleshoot this issue.

I am getting HTTP 401,200 response codes. Same as like http://davenport.sourceforge.net/ntlm.html#ntlmHttpAuthentication

Log:
Current Message: Value was either too large or too small for an Int16. StackTrace:    at System.Convert.ToInt16(Int32 value)
   at System.Convert.ToInt16(Object value)
   at Project.Pages.Layouts.TaskEditForm.GetTaskListInformation()
   at Project.Pages.Layouts.TaskEditForm.Page_Load(Object sender, EventArgs e)

First Message: Thread was being aborted. StackTrace: at System.Threading.Thread.AbortInternal() at System.Threading.Thread.Abort(Object stateInfo)
at
System.Web.HttpResponse.End() at Microsoft.SharePoint.Utilities.SPUtility.Redirect(String url, SPRedirectFlags flags, HttpContext context,
String queryString) at
Project.Pages.Layouts.TaskEditForm.CheckIfTaskFormIsOpenedFromOutLookAddIn() at Project.Pages.Layouts.TaskEditForm.Page_Load(Object sender,
EventArgs e)

Message: Thread was being aborted. StackTrace:    at System.Threading.Thread.AbortInternal()
   at System.Threading.Thread.Abort(Object stateInfo)
   at System.Web.HttpResponse.End()
   at Project.WebParts.Dashboard.Dashboard.DashboardUserControl.Page_Load(Object sender, EventArgs e)
   at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
   at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
   at System.Web.UI.Control.OnLoad(EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.AddedControl(Control control, Int32 index)
   at Project.WebParts.Dashboard.Dashboard.Dashboard.CreateChildControls

Thanks & Regards

MD.Liakath ali