We did a little test of that after the software upgrade. Several users, such as Rebelbase and Miss Marple and a few others who's names escape me right now, volunteered to be suspended to test this. Each of them saw the reason.
However, Darth Sidious did report that sometimes he saw it, and sometimes he saw something like "you must be logged in to post". So there may be some sort of oddity with some sorts of browsers. But if so, a refresh or two does the trick, and it is only intermittent anyway.
Sometimes I have to log in again after posting even when already logged in, but I think that has to do with my software firewall. I would volunteer to be a test guinea-pig for banning, but not sure if you guys would remember me!!