My wife just called from work. She was having trouble installing a program. Usually, you just double-click the .dmg file and drag the mounted image to the Applications folder or click through the installer wizard.
For some reason, this program (some kind of add-on to Adobe Flash) didn’t allow her to install the program, claiming she didn’t have permission. That was a bit odd. So I had her go to the terminal and type groups to see what groups she was in. She was in the all the proper admin groups to allow her to sudo. Then I asked her to go to Applications > Utilities > Disk Utility and do Repair Disk Permissions to see if that’d help. It didn’t.
So I found out, through a bit of Google searching, that you can actually enable the root user and do a full GUI root login. Of course, that meant (since she doesn’t have fast user switching at work) she had to log out of her normal user completely, log in as root user, install the software, and then log out of root user, and log back in as regular user, but at least it worked.
She was a bit confused as to why the regular administrator couldn’t install the program. The only explanation I could give was that the Flash add-on installer may have been written badly so as not to take proper advantage of the sudo‘s ability to temporary escalate admin user privilege.