The Windows Firewall has detected an application listening for incoming traffic.
Process identifier: 3732
User account: SYSTEM
User domain: NT AUTHORITY
RPC server: No
IP version: IPv4
IP protocol: UDP
Port number: 55751
User notified: No
For some reason this event is logged (on Win2k3 in this case), even when the firewall is disabled and the specified process (C:\WINDOWS\system32\someprocess.exe) is setup as an exception.
The only way I was able to get rid of these events was by stopping the SharedAccess (Windows Firewall/Internet Connection Sharing (ICS)) service.
Once stopped, no more 861 events were logged.
This of course disables the firewall, which of course was already OFF in my case.