We are on the same page, let's go with the next step, once you UAC is reset back to its original value (enabled) and you had rebooted the machine, you will start your browser (Internet Explorer, it will be better than anything else at the moment), the you will navigate to your Report Manager by entering its URL, I expect it to be something like: http://DBA/Reports (I am not sure is you are using an instance name.

Now the attached picture show the behavior on my laptop, I get a login screen where I enter my account (without the 'domain' or 'machine' name) and password (I dealt with this issue last week, so, I haven't tried to get rid of this password yet); notice that I drew an arrow to the 'DOMAIN', which is your case, the expected value should be DBA.

After you enter your login credentials, the Report Manager should show you the 'administration' controls, please let us know.