I am able to load the home page now.
I wonder what happened?
Other Ning networks are also affected. You can check status here http://status.ning.com/?cat=1.
I followed the link but it's not terribly specific. Given how much I know about web programming (i.e., very little) I'd probably not understand it anyway.
It's good to know they do sometimes work on weekends (at least, when it's a widespread issue).