Nas' SharePoint Blog helped me with the solution to this issue:

I came accross this error after installing Active Directory on a Windows 2008 Server.  The SharePoint site was not viewable.  To resolve, I did the following:

 

1  Open up IIS Manager and click on Application Pools.

2.  Locate the App Pool account, right-click on it, and select 'Advanced Settings."

3.  Click on the right side of the "Identitity" box to change it.

4.  In the pop up window, re-enter the appropriate App Pool Identity and Password.

 

Make sure the App Pool status is "Started."  If it is not "Started", right-click the App Pool and select 'Start".

 

Thanks Nas!