Url rewriting gives me 404 - File or directory not found.

hi,

ive been rewriting urls for my site and ive used the steps here: http://dotnetguts.blogspot.com/2008/07/url-rewriting-with-urlrewriternet.html

on my local server it works fine, but when i upload it in our web server it gives me the Error '404 - File or directory not found.'
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