IsolatedStorageException in System.IO.Packaging

I made a C# dll to create excel2007 files named excelCreater , and when i call the excelCreater

from a C# exe , it works well . but when i try to call the excelCreater from unmanaged C++ application, i  register the excelCreater as COM, usually it works well too, but while the sheet.xml

in excel file is over 8MBytes , a IsolatedStorageException will be thrown out .

Exception message is "Unable to determine the identity of domain."

Source Code Block:

internal void SavePart(PackagePart partPack, XmlDocument xmlPart)
        {
            StreamWriter stream = new StreamWriter(partPack.GetStream(FileMode.Create, FileAccess.Write));

            xmlPart.Save(stream);    // <---  Exception thrown out here
            stream.Close();
            stream.Dispose();
            Flush();
        }
  

Is there anyone can explain the problem and have solution ?

Thanks alot ! 

i had solved out this problem.

just need to set the C++ project with the /CLR compile option . 

I have the same error in .Net with c# when try to create a word 2010 document with Table contain large string of data in size 14875967