Quite bad issue - a customer has send me an "old fashioned" project with physically merged files. The customer does so for all colleagues, who are still on 2011, so this will not change, as no one will create separate projects for different translators.

Now I cannot open the files within this project as virtual merge - but that is necessary due to many repetitions between files. When I take the files out of the project, I can open them, but not save, the corresponding error message has been forwarded to support. It reads:

<SDLErrorDetails time="3/16/2016 4:32:57 PM">
  <ErrorMessage>Argument '0' is out of range. It should be between 1 and 2147483647.
Parameter name: ChildFileDocuments.Count</ErrorMessage>
  <Exception>
    <Type>System.ArgumentOutOfRangeException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
    <ParamName>ChildFileDocuments.Count</ParamName>
    <HelpLink />
    <Source>Sdl.Desktop.Platform</Source>
    <HResult>-2146233086</HResult>
    <StackTrace><![CDATA[   at Sdl.Desktop.Platform.Validation.WithinRange(Int32 argument, Int32 lowerBound, Int32 upperBound, String name)
   at Sdl.TranslationStudio.Api.Common.MergedFileChildrenPersister.SaveChildFilesDocuments()
   at Sdl.TranslationStudio.Api.Common.MergedFileChildrenPersister.SaveChildFiles(String outputFile, String[] bilingualFilePaths)
   at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.SaveBilingualImpl(String[] bilingualFilePaths, Boolean copy, IJobExecutionContext context, Boolean isAutoSaved)
   at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.Save(IJobExecutionContext context)
   at Sdl.TranslationStudio.Api.Editor.AbstractInternalDocument.SaveJobRequest.Execute(IJobExecutionContext context)
   at Sdl.Desktop.Platform.Implementation.Services.Job.<_worker_DoWork>b__3()
   at Sdl.Desktop.Platform.Implementation.Services.Log.Resources(Object message, Action action)
   at Sdl.Desktop.Platform.Implementation.Services.Job._worker_DoWork(Object sender, DoWorkEventArgs e)
   at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
   at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)]]></StackTrace>
  </Exception>
  <Environment>
    <ProductName>SDL Trados Studio</ProductName>
    <ProductVersion>12.0.0.0</ProductVersion>
    <EntryAssemblyFileVersion>12.2.5087.4</EntryAssemblyFileVersion>
    <OperatingSystem>Microsoft Windows 10 Pro</OperatingSystem>
    <ServicePack>NULL</ServicePack>
    <OperatingSystemLanguage>1031</OperatingSystemLanguage>
    <CodePage>1252</CodePage>
    <LoggedOnUser>AzureAD\JerzyCzopik</LoggedOnUser>
    <DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
    <ComputerName>SPITFIRE</ComputerName>
    <ConnectedToNetwork>True</ConnectedToNetwork>
    <PhysicalMemory>25103188 MB</PhysicalMemory>
  </Environment>
</SDLErrorDetails>

Why is this so? IMHO this is a productivity killer, which I have not supposed to find in Studio...