Hm, you are only disabling the button. I was looking for something like upload picture and show preview and upload again if you want. More like a Ajax-based-user-profile.aspx you have for Ajax Uploader. Minus the resize, I know ASP can not do that on it's own.

About multiple uploader instances, that is really a great pity it is not working, would solve half my and I guess some other people also, problems. Is there any way to implement it, on PHP uploader I found in forum it works. And it was "just" a session issue, so perhaps you could make it work here. This way one could have your instance as form fileupload instance.