NAV 2013 R2 Service Automatically stop

Hello,

any idea on what i am experiencing right now with my NAV APP Server Environment. NAV Service instance automatically stop and i got below errors at event log.

1. Type: Microsoft.Dynamics.Framework.UI.LogicalModalityViolationException
Message: The operation cannot be performed because a modal dialog is open.
StackTrace:
at Microsoft.Dynamics.Nav.Client.WinClient.ExceptionHandler.<>c__DisplayClass6.<DoRethrowWithCatchException>b__4()
at Microsoft.Dynamics.Nav.Client.WinClient.NavClientErrorHandler.ExecuteAndCatchExceptions(Func`1 execute)
at Microsoft.Dynamics.Nav.Client.WinClient.ExceptionHandler.DoExecute(Func`1 execute)
at Microsoft.Dynamics.Nav.Client.WinClient.ExceptionHandler.DoRethrowWithCatchException(Exception exception, Boolean designMode)
Source: Microsoft.Dynamics.Nav.Client.WinClient
HResult: -2146233088

---

Type: Microsoft.Dynamics.Framework.UI.LogicalModalityViolationException
Message: The operation cannot be performed because a modal dialog is open.
StackTrace:
at Microsoft.Dynamics.Framework.UI.LogicalModalityVerifier.VerifyAnyModalFormOpen(LogicalDispatcher logicalDispatcher)
at Microsoft.Dynamics.Nav.Client.NavPropertyBagInvokedActionBase.InvokeCore(LogicalControl logicalControl, Object state, UISession uiSession)
at Microsoft.Dynamics.Framework.UI.LogicalAction.InvokeCoreWithErrorHandling(LogicalControl logicalControl, Object state, UISession uiSession)
at Microsoft.Dynamics.Framework.UI.LogicalAction.DoInvoke(LogicalControl logicalControl, UISession uiSession)
at Microsoft.Dynamics.Framework.UI.LogicalFormActivator.<>c__DisplayClass2.<ValidateAndInvokePropertyBag>b__0()
Source: Microsoft.Dynamics.Framework.UI
HResult: -2146233088

Thanks in advance!
Ed