You run Report Manager and you get a user does not have required permissions / uac error, yet you know you have permissions, in fact you would put money on it…except you stand there locked out of your Report Manager.
A combination of the following is likely to resolve :
1. Disable UAC (Open Control and change User Access Control settings to Never Notify – may require a reboot)
2. Run Internet Explorer as administrator then open the report manager
3. If all else fails, add the url of the report manager to the Local Internet Zones in Internet Explorer, not Trusted Sites.
4. Once logged in, if you are required to me an adminstrator, verify you have the System Adminisator role within the Site Settings link in Report Manager. Additionally set yourself Content Manager permissions at the Home folder level.