Reporting Services Access Error caused by UAC

You might encounter the below error when accessing Report Manager website(which is typically http:///reports).

User 'domain\username' does not have required permissions. Verify that sufficient permissions have been granted and Windows User Account Control (UAC) restrictions have been addressed

When a user with administrator privileges logs in, UAC removes the authorization and access control components that identify an administrator. This causes all the applications to run as if they were launched by a standard user. To work around this, launch Internet Explorer as administrator by right-clicking it and selecting Run as administrator as shown in the screen shot below. 

Now browse to the Report Manager site and explicitly grant full permissions to the account you use to log in. Please note that once you explicitly grant full permissions, you don’t need to launch IE as administrator.

For more details, please follow the instructions in the article (step 7 and 8) - http://msdn.microsoft.com/en-us/library/bb630430(v=SQL.90).aspx