Possible bug
Users can login when Maintenance Mode is active but they cannot logout.
Same problem on my forum too. Whilst in maintenance mode I logged in as a standard user. It returned me to the log in prompt, but at the top of the screen said that I was signed in! I couldn't then sign in as an administrator without clearing the cookies from the browser and starting again.
I'm using 1.1 RC1, this is the only problem i'm having so far, otherwise some excellent software :D
I noticed the Same bug as well..
had to remove the cookies
So upgrade to 1.1 RC2 :) Its much better ;)
I still see this problem in 1.1 RC2