Stack overflow. at System.Threading.TimerQueue.ChangeAppDomainTimer(AppDomainTimerSafeHandle, UInt32) at System.Threading.TimerQueue.EnsureTimerFiresBy(UInt32) at System.Threading.TimerQueue.FireNextTimers() at System.Threading.UnmanagedThreadPoolWorkItem.ExecuteUnmanagedThreadPoolWorkItem(IntPtr, IntPtr) at System.Threading.UnmanagedThreadPoolWorkItem.ExecuteUnmanagedThreadPoolWorkItem(IntPtr, IntPtr) at System.Threading.UnmanagedThreadPoolWorkItem.System.Threading.IThreadPoolWorkItem.Execute() at System.Threading.ThreadPoolWorkQueue.Dispatch() at System.Threading.PortableThreadPool+WorkerThread.WorkerThreadStart()