Andy - Did you enable any new services before it started flaking out on you? Or install any new software? Software firewall perhaps?

No software firewall, removed that a long time ago after moving my firewall needs upstream. I'm regularly installing new software on this machine (it is my main home desktop machine), although I don't remember installing any new services recently.

Sometime else that appears to happen on this machine now is that the network interface numbers exposed via SNMP sometimes change on a restart. When I notice this has happened I have to go back and change my MRTG config files