I just re-read the email we all got sent, and that's partly posted in "Week 6 Important Information" - :
"First, as many of you may know - the very first clue for the new week is going to be presented by Andrew and the team at Mugglenet. Their podcast will be released sometime on this Sunday and you'll want to hear them solve the riddle they've gotten - as the answer to that riddle will be the first password needed to start week 6. Note: that password won't go in the hpquest url. When the quest goes live on Tuesday, April 15 at noon EST - you'll learn what to do with the password then. Go to www.mugglenet.com"
The last three words are in the email but not the post. I assume it's telling us to go to mugglenet tomorrow for the start of the Quest. Although it may just be telling us where to find Mugglenet for the podcast.
And yes, I am trying to go to bed, I'm just too busy answering my mail!