. . . 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."
This message comes up for me only when I try to open one particular thread. Everything else works fine. What does it mean?
Occasionally the mods will disappear a thread, if it was started by a spammer or a sock. That may be what happened to the thread you’re trying to access.
Generally that means the thread has been moved to the cornfield, aka disappeared.
This clearly wasn’t a spammer. Maybe the thread was a little argumentative, but nothing worth closing, let alone disappearing.
I edited my post to add “or a sock.” Was it started by a poster you recognize?
In before the thread is closed…
If it is this one, a brand new poster came in ranting and raving in huge black type for like 4 pages. 10 minutes later the OP (also new) chimes in. Smelling a sock, I noted the post in question to the mods, and I come back and they and the thread are all toast. 
I don’t remember the OP, but it was one of those threads where a guy is theorizing/complaining about the injustice of relations between men and women. Nothing really that controversial, or a reason to suspect a sock.
I’m fairly certain there were three socks in that thread. But I wish we could keep Chad Thundercock just for his name.
I didn’t see the four-page rant, but that could’ve been it. I’ve never had this message before; I guess that’s as good a reason as any.
4 screens (=pages), more like.
It’s still a shame when that happens because non-socks have posted and some reasonable conversation was being had.
Chad Thundercock. You NEVER forget Chad Thundercock. If there is any discussion from now on regarding male/female relations, I will always ask myself “what would Chad Thundercock do”?
He was no sock. At the least a liederhosen. Maybe even a full length stocking.
Since the question in the OP has been answered, let’s close this. The message appears when a thread has been removed from public view for some reason.