So let me get this straight; to play as a guest, you need the person in question to log in to Battle.net. If this is the case, what is the purpose of the Play as Guest function if you need to know a SC2 player's user name and password? As it stands right now, Play as Guest works only as a crappy version of the real game, considering it has no online play or achievements. And if you need to log in to BNet to play, why on EARTH do they give you three Guest files?
Once you activate SC2 on the PC, you can play as guest and do the single player campaign, multiplayer vs AI and challenges. You don't need an internet connection or to log-in to Bnet to play as guest. You do need to log-in every 30 days to re-activate the PC. The guest account, I reckon, is useful for people living in the same household who won't use multi-player mode.
Then I suppose something is horribly wrong with my copy. I can only use guest if I log into a BNet account (my brothers), log out, and play. If the game should close, it will give me that error message about logging into BNet first.
Hmm, yeah. Issue with your PC. I had no problems playing as guest on any of the computers at home when our modem died (no internet for 3 days ) I suggest contacting Blizzard support.
rui: It seems other people are reporting similar problems to Slartibartfest lately. I could only thing that the computer, trying to connect to a network is a problem. I wish Blizzard would just make everything about the game work on port 80
But the thing is, he has no problems logging in to Blizzard. The issue seems to be getting the PC to keep the activation. Blizzard supposedly fixed this in one of their patches. I guess they still haven't fixed it for all set-ups.