Hey, There's a bug affecting the ability to read Announcements via the New Posts page. If the announcement is accessed from a forum page, it'll work then. Martin.
If it makes you feel better, I'm an admin, and I get the same error. As far as I know, it's a longstanding bug in vBulletin. I know it only affects some people and I'm not sure what exactly causes it. But it will soon be solved with the switch to the new platform.