The server seems to be in a bit of a clusterfuck, but unit 1 was interesting. Rot13: V npghnyyl zrffrq hc ba gur Puvarfr "fbhc/zvk" pbeerfcbaqrapr dhrfgvba, naq nz srryvat dhvgr flzcngurgvp sbe Tbbtyr Genafyngr evtug abj. :)
Yeah, I messed up with one of those too, but IIRC it was more a case of not noticing/missing one line.
(Also, part of the problem is that some of the symbols were partly covered by the buttons you could select, so..)
Here you go: http://www.ai-class.com/
They're still working out kinks in the site, and no homework is up yet, but the initial set of lectures (really really basic "what is AI/welcome to the first day of class" type stuff is up), so if you signed up, then sign in and hopefully the site will work for you.