I am running an ISA 2004 Server on a 2003 SP2 box. This box is publishing HTTPS for OWA and I noticed that sometimes OWA would be unresponsive from the outside. On closer inspection, the ISA service would get a "Resource Allocation Conflict" error message under monitoring.
I did some research and running "netstat -ano | findstr :443" produces
TCP 192.168.1.2:443 0.0.0.0 LISTENING 3648
Going to task manager and looking up process ID 3648 brings up the wspsrv.exe service.
A reboot of the box will fix the issue until it reoccurs. The box does not run IIS or anything else that I can think of that would host HTTPS services. It has been running just great for years until recently.