I had previously upgraded my MacBook Pro (original unibody model) to Mountain Lion with no apparent issues. I have two Users, both with Admin status and everything appeared to function as before.
I just traded in my old MacBook Pro for a new current model Retina MacBook Pro, using Migration Assistant upon first startup to move everything over from the older machine. Most everything has been seamless - except for Permissions.
I started seeing messages appear indicating I didn't have permission to open files, run apps, delete files, etc. Looking at Get Info, I found Sharing & Permissions was only set up for (if I recall correctly) Admin, Administrator and something called Wheel. I solved the permissions issue while logged in as the primary User by adding both Users to the Sharing & Permissions section of the Info screen for the entire hard drive, giving them Read & Write access, and selecting Apply to enclosed items... That seems to have solved the issue for the primary User.
But then I tried working logged in as the secondary User. I started getting messages indicating I could not save a file I had just modified because I did not have permission, and that I should contact the Administrator. Well, that's me. So I tried the same thing that I did logged in as the primary User, but there was no change. I still can't save a modified file logged in as the secondary Admin User.
I haven't found anything that addresses this - except to learn where the Wheel User originated. Can someone point me in the right direction to where I can learn how to gain full, unlimited access to my own computer - under bothe User accounts?