WPF crashing by Environment.FailFast

I am working on WPF application built for Kiosk (Touch Screen). We build Virtual Keyboard for ourselves. There is one screen we list some items (max of 4 items) using DataGrid control which has a TextBox. The virtual keyboard shows on focus (thats how it built). When we make selecting different items randomly, the application crashes without reaching the generic exception handler. This issue is repeatable on Touch screen, but not in regular screens. The event log shows the below, ``` Application: CashNGo.WPF.exe Framework Version: v4.0.30319 Description: The application requested process termination through System.Environment.FailFast(string message). Message: Unrecoverable system error. Stack: at System.Environment.FailFast(System.String) at MS.Internal.Invariant.FailFast(System.String, System.String) at MS.Internal.Invariant.Assert(Boolean, System.String) at System.Windows.Documents.TextStore.VerifyTextStoreConsistency() at System.Windows.Documents.TextStore.GrantLock() at System.Windows.Documents.TextStore.GrantLockWorker(LockFlags) at System.Windows.Documents.TextStore.RequestLock(LockFlags, Int32 ByRef) at MS.Win32.UnsafeNativeMethods+ITextStoreACPSink.OnSelectionChange() at System.Windows.Documents.TextStore.OnSelectionChanged() at System.Windows.Documents.TextSelection.System.Windows.Documents.ITextRange.NotifyChanged(Boolean, Boolean) at System.Windows.Documents.TextRangeBase.EndChange(System.Windows.Documents.ITextRange, Boolean, Boolean) at System.Windows.Documents.TextSelection.System.Windows.Documents.ITextRange.Select(System.Windows.Documents.ITextPointer, System.Windows.Documents.ITextPointer) at System.Windows.Controls.TextBox.Select(Int32, Int32) at System.Windows.Controls.TextBox.set_CaretIndex(Int32) at Common.Controls.SoftKeyboard.<.cctor>b__1c(System.Windows.Controls.TextBox) at System.Windows.Input.DelegateCommand`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].Execute(System.__Canon) at Common.Controls.SoftKeyboard+<>c__DisplayClass5.<SoftKeyboardFocus_Changed>b__0() at System.Windows.Threading.Dispatcher.Invoke(System.Action, System.Windows.Threading.DispatcherPriority, System.Threading.CancellationToken, System.TimeSpan) at System.Windows.Threading.Dispatcher.Invoke(System.Action, System.Windows.Threading.DispatcherPriority) at Common.Extensions+<>c__DisplayClass1.<DelayedInvoke>b__0(System.Object, System.EventArgs) at System.Windows.Threading.DispatcherTimer.FireTick(System.Object) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate, System.Object, Int32) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(System.Object) at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean) at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean) at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef) at MS.Win32.HwndWrapper.WndProc(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(System.Object) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate, System.Object, Int32) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate) at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(System.Windows.Threading.DispatcherPriority, System.TimeSpan, System.Delegate, System.Object, Int32) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr, Int32, IntPtr, IntPtr) at MS.Win32.UnsafeNativeMethods.DispatchMessage(System.Windows.Interop.MSG ByRef) at System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame) at System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(System.Object) at System.Windows.Application.RunInternal(System.Windows.Window) at System.Windows.Application.Run(System.Windows.Window) at System.Windows.Application.Run() at CashNGo.WPF.App.Main() ``` I did some search and found http://social.msdn.microsoft.com/Forums/vstudio/en-US/dfbd2526-8953-4ce8-97c2-43246fd251c0/wpf-framework-crashing-on-setting-foxus-in-textbox?forum=wpf which is exactly the same exception. Any suggestion would be helpful.