Do not have permission to access this page

I don't know where to post this but maybe one of the moderators will read it and can answer the question. In my email, I clicedk on a link to view a response to a thread that I am subscribed to. But I got the message that you see below. This is the first time that this has happened.

Frank1, you do not have permission to access this page. This could be due to one of several reasons:

1. 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?
2. If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

The few times that's happened to me it's because the thread was removed.

Has happened at least twice while I was in the middle of typing a reply to the thread

If a thread is removed or deleted, you will get that.

Edit: And now I see that Fseal has beat me to it.

I've just edited the default error message to mention that the thread may have been removed or deleted.

Thanks for the reply. I though maybe I was kicked out. I fell better now.