Hi, I was also facing this issue after proper unzipped the nopcommerce folder in local directory and when i run the application in VS2012 it successfully worked for nop.web solution folder but when i tried to log into admin section by setting the start-up project nop.Admin it did'n work.
After googling nothing worked, then i checked the database permission tables and tried one more attempt too login by [email protected] and admin password it showed me common page likewise storefront page but then i changed the Url by adding http://localhost:yourport/Admin/ then it brought me into the admin section.
Hope somebody will take help from this issue and will save his time.