> 
> Without deleting latest.zip the problem disappears. I suspect 
> Göran's suggestion of a FileStream hanging around is correct?

I'm not sure I understand what you mean by that first sentence.

> 
> Does BFAV keep a FileStream open for its entire life, or just 
> for the processes involving reading/writing? I mean, when you 
> hit load updates, does BFAV then open a FileStream on 
> latest.zip and then clean up that FileStream after?
> 

It *should* be doing that; perhaps there is not cleanup ensure: block in every place there ought to be.