I have read that when "Play as Guest" mode is selected, Starcraft II campaigns can be played without achievements being recorded to your profile.
Every time I click to the "Play as Guest" button, it tells me to authorize my game client. Then I login. Because game does not allow me to switch to guest mode I exit the game. I relaunch the game. And finally I can play as guest without internet connection.
At the moment I am sharing a 3G modem with my father so I can't be online all the time, and I am sick of doing this "login, close, open" every time.
Do you have any idea what might be wrong?