virtual host stopped answering https

I've seen this on systems experiencing a memory leak or other internal issues. You could SSH to the box but not pass any traffic through VIPs. Was it just this VIP or all VIPs? Any other indications? If you're still using this dinosaur box and it happens again, look at system memory and CPU (tmstat, top, bigtop for starters). Also do a TCPDUMP on the external and internal interfaces to see if traffic is getting to or leaving the box.