Hi, I am facing weird problem while running regression tests on my WPF Application. I am getting AccessViolationException with different stacktraces each time. First : Message :Attempted to read or write protected memory. This is often an indication that other memory is corrupt. StackTrace : at MS.Win32.PresentationCore.UnsafeNativeMethods.MILUnknown.Release(IntPtr pIUnkown) at MS.Win32.PresentationCore.UnsafeNativeMethods.MILUnknown.ReleaseInterface(IntPtr& ptr) at System.Windows.Media.SafeMILHandle.ReleaseHandle() at System.Runtime.InteropServices.SafeHandle.InternalFinalize() at System.Runtime.InteropServices.SafeHandle.Dispose(Boolean disposing) at System.Runtime.InteropServices.SafeHandle.Finalize() Source :PresentationCore Type : System.AccessViolationException. Second : Message :Attempted to read or write protected memory. This is often an indication that other memory is corrupt. StackTrace : at MS.Win32.PresentationCore.UnsafeNativeMethods.IMILBitmapEffect.GetOutput(SafeHandle THIS_PTR, UInt32 uiIndex, SafeMILHandle pContext, BitmapSourceSafeMILHandle& ppBitmapSource) at System.Windows.Media.Effects.BitmapEffect.GetOutput(SafeHandle unmanagedEffect, Int32 index, BitmapEffectRenderContext context) at System.Windows.Media.Effects.BitmapEffect.GetOutput(BitmapEffectInput input) at System.Windows.Media.Effects.BitmapEffectState.GetEffectOutput(Visual visual, RenderTargetBitmap& renderBitmap, Matrix worldTransform, Rect windowClip, Matrix& finalTransform) at System.Windows.Media.Effects.BitmapEffectVisualState.RenderBitmapEffect(Visual visual, Channel channel) at System.Windows.Media.Effects.BitmapEffectContent.ExecuteRealizationsUpdate() at System.Windows.Media.RealizationContext.RealizationUpdateSchedule.Execute() at System.Windows.Media.MediaContext.Render(ICompositionTarget resizedCompositionTarget) at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget) at System.Windows.Media.MediaContext.AnimatedRenderMessageHandler(Object resizedCompositionTarget) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter) at System.Windows.Threading.Dispatcher.Invoke(DispatcherPriority priority, Delegate method, Object arg) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.RunInternal(Window window) at System.Windows.Application.Run(Window window) at System.Windows.Application.Run() at Main() Source :PresentationCore Type :System.AccessViolationException In Application Event Log I found following entries : Dispatcher processing has been suspended, but messages are still being processed. Faulting application **.exe, version 1.0.0.*, stamp 4c08d288, faulting module wpfgfx_v0300.dll, version 3.0.6920.1427, stamp 488f3056, debug? 0, fault address 0x0012ec36. My Application uses Dispatcher from another thread, to change the values of the controls , enable - disable those, change visibility etc., the thred is run multiple times in a second. Please let me know if anybody has faced this problem? Thanks in advance, -Prasad