Error when opening a file with Studio: "Value cannot be null. Parameter name: array"

 I created a project containing two small docx files (JA to EN) and when I try to open the files I get this error message and the files cannot be opened. Please help. Thanks in advance. Below is the copy of the error xml:

<ErrorMessage>Value cannot be null. Parameter name: array</ErrorMessage>


-<Exception>

<Type>System.ArgumentNullException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>

<ParamName>array</ParamName>

<HelpLink/>

<Source>mscorlib</Source>

<HResult>-2147467261</HResult>


-<StackTrace>

<![CDATA[ at System.Array.ConvertAll[TInput,TOutput](TInput[] array, Converter`2 converter) at Sdl.TranslationStudio.Plugins.AnyTM.MixedSource.MixedSourceViewModel.SaveSettings(Document doc) at Sdl.TranslationStudio.Plugins.AnyTM.MixedSource.MixedSourceViewModel.OnActiveDocumentChanged() at Sdl.TranslationStudio.Plugins.AnyTM.MixedSource.MixedSourceViewModel.Editor_Opened(Object sender, DocumentEventArgs e) at System.EventHandler`1.Invoke(Object sender, TEventArgs e) at Sdl.Desktop.Platform.Extensions.EventsExtensions.Raise[T](EventHandler`1 e, Object sender, T eventArgs) at Sdl.TranslationStudioAutomation.IntegrationApi.EditorController.OnDocumentOpened(IDocument document) at Sdl.TranslationStudio.Api.Editor.DocumentEventHandler.Invoke(IDocument document) at Sdl.TranslationStudio.Editor.EditorService.OnDocumentOpened(IDocument document) at Sdl.TranslationStudio.Editor.EditorService.document_Loaded(IDocument document) at Sdl.TranslationStudio.Api.Editor.AbstractInternalDocument.OnLoaded() at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.OnLoaded() at Sdl.TranslationStudio.Api.Editor.AbstractInternalDocument.AfterLoad(IJob job)]]>

</StackTrace>

</Exception>