Had an issue today while setting up my test environment at home. I was trying to browse to a newly created site collection using the Web Server’s IP address. The Web Server prompted me for username/password (note, the PC I am connecting from is not on the domain). After entering the correct credentials, I would get a ‘page not found’ error.
After some investigation, I found that you need to create an alternate access mapping for the web application under Central Administration. After adding the IP address ‘http://10.x.x.x’, I was immediately able to browse to my site collection (no IISreset needed).