Hi, thanks for your reply pamelaz!
I have tried using Chrome v. 23 and IE 9.
I am not clearing my cookies / cache or running PC maintenance programs on a basis that would cause this.
I can "reset" my password, then log off and try to log on within one minute, and I am not logged in.
What I also think is strange is that I don't get any error message at all when I am not logged in, which seems unusual to me.