Back to School Challenge NOT Working

Back to School Challenge - I have signed up for this & am doing fairly well. My problem is that I can no longer access the Back to School Challenge page. I can get to any other wiki page except that one. Any ideas? I've cleared cookies & cleared my cashe like I was told & still nothing. I can't get any further points if I can't access the page. :) A few times I've been able to sign in & then it throws me back to the sign in page again, but usually I can't even get to the sign in page for the challenge. This is really bothering me! I've been trying for days to get on. Thanks for any help!!!