httpwebrequest

I have a vb.net web service application. Using IIS 6, I have configured a virtual directory that I wish to httpwebrequests to both place and download files. My application works fine when I run my application on my development machine which also contains the web server. When I run my vb.net application on another computer on the internet, I get the following error when I attempt to move files via http:

(503) Server Unavailable

I would certainly appreciate any ideas on what the problem is.

Thanks,

Fred