The IP is actually not blocked, only when I try to go to the clear expired cache menu item. All other navigation works fine.
When I go to admin tools though, there is the red button for "unblock my IP" which I have clicked on, though it doesn't go away afterwards (although I don't think it ever does after I have legitimately blocked myself out, usually when I've timed out).
I have admin tools installed on many sites and I'm not seeing this behavior on the other ones.