Hi Adam,
I got the error message I mentioned earlier about Windows\TEMP. This is the same case we talked about in http://cutesoft.net/forums/thread/32331.aspx.
You looked at my machine and tried changing permissions yourself but the only thing that worked was changing impersonate to false in the web.config.
I can let you back onto my machine if needed but you should be able to reproduce this yourself simply by setting impersonate to true in a test web application.
Thanks,
Mike.