The permissions granted to user ' are insufficient for performing this operation. (rsAccessDenied)"}

It's because of lack of privilege for the user you are running the report builder, just give that user or a group a privilege to run report builder. Please visit this article

Or for shortcut:

1. Start Internet Explorer using "Run as Administrator"
2. Open http://localhost/reports
3. Go to the Properties tab (SSRS 2008)
4. Security -> New Role Assignment
5. Add DOMAIN\USERNAME or DOMAIN\USERGROUP
6. Check Report Builder

I know it's for a long time ago but you (or any other new comers) can resolve this issue by

1. Add the [Domain\User] to Administrator, IISUser, SQLReportingUser groups
2. Delete Encryption Key in SSRS configuration tools
3. ReRun the Database Change in SSRS configuration tools
4. Open WebServiceUrl from SSRS configuration tools (http://localhost/reportserver)
5. creating Reports Folder manually
6. go to Properties of created folder and add these roles to security (builtin\users , builtin\Administrator, domain\user)
7. Deploy your reports and your problem resolved

I have SQL2008 / Windows 2008 Enterprise and this is what I had to do to correct the rs.accessdenied, 404, 401 and 503 errors:

• Added NT Users to SQL Report Server Users and IIS_USR Group
• I changed SQL Reporting Service to Local account (it was Domain with Local Admin)
• I deleted encryption key in Reporting Services Configuration (last tab on the list)
• and THEN it worked.