I tried to post in a thread and it wouldn't allow me although I am logged in. Some threads are fine though. Why is that?

Is my account being disabled? I have 1000+ posts so I don't think I don't have enough privilege to reply? What is happening here?
Here is the message shown.
Potter, you do not have permission to access this page. This could be due to one of several reasons:
Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.