thanks for the example peter, by way of closing the thread here was my response;
So the problem you're seeing here is that the page is refreshed when the form is invalidated.
Refreshing the page results in the File Upload field being refreshed.
So, I think what you want to do is add "more fields". Basically you want a display field which shows the name of files already uploaded.
If you show the name, then it's there for the refresh ? and also if the user edit's the record.
cheers
Bruce