I've used Procmon to identify that NT AUTHORITY\NETWORK SERVICE is being denied access to certain files on my local web server. Occasionally this happens on my compressed css and js files (static.min.js, static.min.css) and at the moment it is happening with newly added image files. I have confirmed through right-clicking on the files, choosing properties and selecting security that Network Service does have read access to the files.
I am using IIS7 and the site is ASP.NET 2.0.
The site operates correctly other than these particular files.