Howard is right (not uncommon)
You might try turning off all the "usual suspects" until it works. For example switch your apache back to port 80 then disable Skype if you having it running. If that makes no difference turn off apache and then make a request for http://localhost. You should get an error, if you don't then you have another web server running (typically IIS). Let us know the result of trying those ideas. Do some web searches on the topic, many other people have had a similar problem. Are you running Windows?