Studio is prompting me the said issue. The error details are es follows:

<SDLErrorDetails time="03.05.2017 13:44:23">
  <ErrorMessage>Object reference not set to an instance of an object.</ErrorMessage>
  <Exception>
    <Type>System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
    <HelpLink />
    <Source>Sdl.Desktop.Platform.WinForms</Source>
    <HResult>-2147467261</HResult>
    <StackTrace><![CDATA[   at Sdl.Desktop.Platform.WinForms.DockingViewContentControl.CanShowViewPartWithoutHidingAnotherViewPart(IViewPartReference viewPartToShow, IViewPartReference viewPartThatCannotBeHidden)
   at Sdl.Desktop.Platform.AbstractViewWithParts.CanShowViewPartWithoutHidingAnotherViewPart(IViewPartReference viewPartToShow, IViewPartReference viewPartThatCannotBeHidden)
   at Sdl.TranslationStudio.Editor.EditorService.ShowTranslationMemoryWindow()
   at Sdl.TranslationStudio.Editor.TranslationEditor.SideBySideDocumentEditingView.Document_TranslatingSegment(ITranslatableDocument document, ISegmentContainerNode segment, ITranslationResults results)
   at Sdl.TranslationStudio.Api.Editor.SegmentTranslationEventHandler.Invoke(ITranslatableDocument document, ISegmentContainerNode segment, ITranslationResults results)
   at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.OnTranslatingSegment(ISegmentContainerNode segmentNode, ITranslationResults results)
   at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.TranslateSegmentWorker.Translate()
   at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.TranslateSegment(ISegmentContainerNode segmentNode)
   at Sdl.TranslationStudio.Editor.TranslationEditor.SideBySideDocumentEditingView.TranslateActiveSegment()
   at Sdl.TranslationStudio.Editor.TranslationEditor.SideBySideDocumentEditingView.TryTranslateActiveSegment()
   at Sdl.Desktop.Common.DelayedExecutable.Execute()
   at Sdl.Desktop.Common.DelayedExecutionEngine.Timer_Tick(Object sender, EventArgs e)
   at System.Windows.Forms.Timer.OnTick(EventArgs e)
   at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)]]></StackTrace>
  </Exception>

System details: SDL Studio 2014 SP2 - 11.2.4435.12

The last Windows update seems to have been 2 April, but the issue has not occured until 2 May.

The file to be translated is Word docx I received from the customer. It has worked smoothly a 1000 times before.

Anyone? Please.