Member claims he doesn't have rights to post

I have a member that claims he does not have the rights to post. He says that every time he tries to start a new topic, he gets a message that says he does not have the rights.
I have checked his rights in the AP and everything in there is allowing him to post, but he says he still can't.
Somehow he managed to post five or six times the other day and now says he can't post again.
What could be the problem?

Ask the member if you can log onto the forum using his/hers account and see if the problem occurs. After you try it, tell the member to change hers/his password.