I am using a script manager for ASP.NET MVC to combine and compact CSS files and JavaScript files for pages on a website. For the most part this works as expected, however there are times (couple of times per week) when the HTTP handler responsible for returning the content returns an empty response and so pages load without any CSS - the HTML returns and the images load as well. When this happens, refreshing the page does not resolve the problem, while resetting IIS always resolves the problem. Also, without resetting IIS, after some time the problem stops.
Normally the script handler logs errors, however there are no errors logged during the issue. It seems as if the handler is never invoked. There are no failed request logs generated by IIS.
I monitored resource usage when this was happening and did not notice anything out of the ordinary. The web server is running IIS 7 and has low CPU usage. I increased some parameters in IIS settings regarding the number of allowable requests to process, the problem still exists though perhaps less frequent. The website receives about 1.5 million pageviews monthly.