I don't think it's a time thing, necessarily. I'm 99% sure it's somehow related to the domain/hostname.
Here's what I know... the site in question has several domains all pointing to the same site. They would prefer to have everything go to grassrootsmotorsports.com. In the punbb admin, that's the domain that's set. Somewhere in the dark mists of time, the server hostname was set to www.grmotorsports.com.
I set up an .htaccess file to route all traffic to the preferred domain. Anyone who comes to grmotorsports.com, or any www subdomain, gets routed to grassrootsmotorsports.com. With the htaccess rewrite rule turned off, if you go to the grmotorsports.com domain all kinds of things (mostly admin, editing, and login status) go funky. But, if I turn it off, show new posts works.
When I turn the rewrite rule on, everything is stable except "show new posts". I'm thinking it's that mismatch between the hostname and domain name, although it could be my htaccess file. Unfortuntately, I don't currently have access to the htaccess to paste it in here.