I had the same problem and received the message, "Internet Explorer Cannot Display This Web Page." I solved the problem in one minute. I have Zone Alarm free firewall but this may work in other situations too.
Go to
www.avast.comClick on Support
Under Technical Support, click on Support Center
Half way down the page, look at Popular Knowledgebase Articles
Click on Configuration of the Web Shield HTTP Proxy
Follow the quick and easy steps, depending on your type of connection
Before making changes, write down your original settings
Then try connecting to the Internet to browse after making the small changes. The whole thing took one minute to do and I am now able to access any Web site I want.