What browser are you using? Are you closing the browser window (all of them) and then re-launching it? Did you clear the cache for the browser? Are you using any addons like auto form fill (or anything similar)?
Did you log out of the router (initially) or did you just navigate away from the router's page?
Chrome/firefox... happens on both of them, on different computers, no addons, no autofill, and yes I always log out.
Look, this happened now, today. No problems before.
This guy is experiencing the same: http://www.snbforums.com/threads/cant-login-to-router-still-routing.34735/
Strange...