XmlException only during high usage DataContractSerializer - serialization

Question

I have a working windows 8 caching solution using DataContractSerializer that raises a XmlException "Unexpected end of file" only when the UI is being used 'quickly'.
public static class CachingData<T>
{
public static async void Save(T data, string filename, StorageFolder folder = null)
{
folder = folder ?? ApplicationData.Current.LocalFolder;
try
{
StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
using (IRandomAccessStream raStream = await file.OpenAsync(FileAccessMode.ReadWrite))
{
using (IOutputStream outStream = raStream.GetOutputStreamAt(0))
{
DataContractSerializer serializer = new DataContractSerializer(typeof(T));
serializer.WriteObject(outStream.AsStreamForWrite(), data);
await outStream.FlushAsync();
}
}
}
catch (Exception exc)
{
throw exc;
}
}
public static async System.Threading.Tasks.Task<T> Load(string filename, StorageFolder folder = null)
{
folder = folder ?? ApplicationData.Current.LocalFolder;
T data = default(T);
StorageFile file = await folder.GetFileAsync(filename);
using (IInputStream inStream = await file.OpenSequentialReadAsync())
{
DataContractSerializer serializer = new DataContractSerializer(typeof(T));
data = (T)serializer.ReadObject(inStream.AsStreamForRead());
}
return data;
}
}
e.g. user clicks on item in list CachingData.Load is called async via await, checks for FileNotEoundException and either loads the data from disk or from the network, serialising on completion.
After first loaded user selects another item in the list and cycle repeats.
The problem occurs when "After first loaded" becomes "does not wait for load" and the item selected is not available cached.
Not quite sure how to proceed or even how to debug, hoping that just ignoring will allow the app to continue(just withough the nice speed increase of caching)