Dude, add 1 more thing to the FAQ... Well this happens to me before and alot of ppl kena also~ So this might help

If they cannot play AI or Multiplayer...

When they click play with AI, it comes out 'content not found'... When they play on multiplayer, it always hangs and says 'unable to play while downloading'...

This happens to some unlucky fellas (such as me) with a broken cd with no MAPS inside...

All they need to do is a complete reinstall.. Whereby they need to delete all starcraft 2 folders including the ones in mydocuments and in applicationfolder...

Then install with a friend's working cd... Or download from internet...

Problem solved