Cannot Access SharePoint Web Sites from SharePoint Farm

Issue

Recently was having a pretty rough time configuring eDiscovery on a SharePoint 2010 farm. I did not create the environment and we were experiencing some rather weird issues.

1. When we are on the Central Admin machine, we cannot navigate to any web application. It was worse, we could not access the web applications from any of the machines in the farm. None.
2. We thought well not a big deal, the web applications can access to other places. So we went to General Settings to Configure some Send To Addresses. However the validation routine for the addresses would not work.
3. eDiscovery would flat out not work either. If we went to Monitoring to run the Search and Process job (which runs the eDiscovery piece) nothing would happen. When we go into the ULS logs, the websites where the data was found were not accessible. Again the Central Admin machines could not see the web applications.

Resolution

Well it turns out there was some obscure issue with the configuration of the machines. For some reason a loopback check had been enabled and was blocking the ability to navigate to the sites. We found the following reference (method 1) which resolved the issue - http://support.microsoft.com/kb/896861

So what I learned is you cannot get by not being able to access the web applications from the machines where services are hosted. You will also need to run this configuration on each and every machine in the SharePoint farm if this is an issue.