Cannot access Reporting Services Reports Website even starting IE as administrator

I have installed  SQL Server 2008R2 Developer Edition with Reporting services on a standalone (not in a domain) PC with Windows 7.

When I try to access the Report Server page using either one of the following URLs:

http://machineName/ReportServer

or

http://localhost/ReportServer

I have read similar questions and tried to perform the steps of the solutions. I am the administrator of the computer and I have started IE (8 and since recently 9) "as administrator.

Regardless of this, whenever I point the browser to one of the above two links I get the same error message:

"User Machine\User' does not have required permissions. Verify that sufficient permissions have been granted and Windows User Account Control (UAC) restrictions have been addressed." I have also added Machine and localhost as trusted accounts. I also tried turning off UAC, but with the same result.

I would greatly appreciate getting help on this issue -- is this a known issue and what fix/workaround to use?

Thanking you in advance, Ann.