Re: Admin apps problem [duplicate from General]
It sounds to me like "running everything with sudo" and adding yourself to the root group has pretty much borked the security system. I might be wrong; but it sounds like something you've run as 'sudo' has changed the permissions on some crucial per-user files. This is completely theoretical guessing on my part.
I have no idea how to find out what files are wrong and whether it can be fixed. The obvious answer is to reinstall, and try to work inside the security system more in future rather than constantly subvert it. A lot of Linux programs simply don't expect to be run as root with sudo and can't be expected to behave properly when they do; I've not paid any attention to what my programs might do if run with sudo.
The other thing to try is to back up your personal files (not settings) and make a new user account that has access to sudo (has "Administer the System" permission in the Users And Groups program). This new account should, if I'm right, work correctly, and you can copy across your personal files again. Try it.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.