Hi Bruno, your post is not clear about the problem. You are saying that you can no longer Change Roles when editing? Or you mean that during the upgrade, your role seems to have lost its administration capabilities? I am going to assume that as you say that the Admin links are not available, then it is the second you mean.
Go into the database, using phpMyAdmin if you have it, look for the User table and find your userid number.
Go to the Roles table and make sure you understand what Roles you should have, usually just 1 Manager, and 2, Course Creator, but sometimes 3, never anything lower.
Next, go to the Role_Assignments table and check what Roles you have in each context. Look at every line your userid number appears. For the first time it appears it should read
roleid = 1, contextid = 1 and your userid
The second time it appears will probably be:
roleid = 1, contextid = 2 and your userid.
I am not sure if this next part is important or not, but look anyway. Go to the role_context_levels and check that the roleid = 1 and the contextlevel = 10. I have several different contextlevel assignments in my database for my roleid and not sure why.
This should be enough to get you out of trouble anyway. Be careful, if you get this wrong, you can make an unholy mess of your database. If you have another administrator account, or if you have another person as administrator, you might want to get them to look and see if they are having the same problems.
EDIT: Something I have done in the past has been to create a second administrator. While it is a dummy account, it has full admin rights, and it was always in my mind that it might be useful precisely in this kind of situation, maybe. As I would be the only one who knew who Emily McGillycuddy really was, there was not going to be a problem - unless a new admin might try to delete her - which would be easily undone. As I have never had the need of her, I dropped it some time back, but now I am thinking I might reinstate her as I am going to be upgrading my two Moodles in January. Thanks for the tip off, Bruno... cheers.