T3200M stuck at "invalid username" and "logged in as: admin"

Hi there, I have had a recurring problem for some time now, whenever I try to log into my T3200M, it always says "invalid username and password" above their fields, and below it says "You are currently logged in as: admin". I am unable to find anyway to get back to a valid login, barring power-cycling the box. The "logout" button does nothing (the HTML requires the existing session number to work), none of the buttons at the top work, and I cannot re-enter my username and password to login again.

Is anyone aware of this issue and whether there is a work-around.