No subject

[pkaplan1 at comcast.net]

I noticed the other day that the "Important security updates" box in the 
Update tab for managing the repositories in Adept was not checked.

In fact, I couldn't check it; whenever I release the mouse button, it becomes 
unchecked.

I had a 3rd party repository enabled (security.ubuntu.com), but unchecking or 
removing it didn't solve the problem.

Can anyone tell me what's happening and how to correct?
Paul