WinRT Accessing same file twice giving Catastrophic failure error

I have created method to save InkManager in local Storage the code is as below. But When I am accessing it twice its me error...

Catastrophic failure (Exception from HRESULT: 0x8000FFFF (E_UNEXPECTED))

What could be the possible error?

The code:

try
{
    StorageFile myMerge = await ApplicationData.Current.LocalFolder.CreateFileAsync("sign.png", CreationCollisionOption.ReplaceExisting);         

    using (IOutputStream signature = await myMerge.OpenAsync(FileAccessMode.ReadWrite))
    {
        if (signature != null)
        {
            await _inkManager.SaveAsync(signature);

            signature.Dispose();
        }
    }
    return myMerge;
}