Lost Admin Privileges

I tried updating iTunes earlier this week and it wouldn't let me. After some investigation, turns out my log in is not recognizing my admin privileges.

I have tried the instructions here http://macoshelp.blogspot.com/search/label/administrator but it did not work. I've also tried launching through my install DVD and resetting the password.

The odd thing is, even when I am in as the system administrator, I do not have option to check the box to "allow user to administer this computer." I also do not have the option to check this box when I am logged in as me. Under the accounts, my log in says admin.

I've tried a repair disk and repairing the permissions.

Any advice? Thanks