Are you getting a proxy error?
The error you are seeing is usually caused by outdated information stored in your browser cache. To clear this out, follow the instructions for your browser on this site: http://www.refreshyourcache.com/en/home/ . As you go through the steps, be sure that you clear ALL information from the cache, rather than just information from the last day, last week, etc. Also, after clearing the cache, RESTART your computer before trying again to access the library resources.