How can I get back to receiving the site the way I used to ...... showing a list of the latest activity?
You can't. It's a symptom of the poorly maintained Ning platform. Classicbanjo ning site having the same issues, along with many other ning sites.
Figures! As soon as you say I can't, it's back to the way it was, with a list of the latest activity. But it's inconsistent and I imagine as soon as I return from sending this response, I'll get the list of Forums, instead.