Apache :: Cannot Start Server - No Listening Socket Available

I'm running Apache 2.2 on Windows 7. I'm a casual user of the Apache server, and the server I'm running is only used to develop a Silverlight application on the local machine, nothing more. The following problem is apparently a non-systematic error (sometimes the server can startup, sometimes it cannot. If it cannot, it sometimes can after a reboot (a service startup race condition?))

I get error when starting the server: "The requested operation has failed!"

When I run "http.exe" from a command prompt I get:

Quote:

httpd.exe: Could not reliably determine the server's fully qualified domain name, using 10.0.0.100 for ServerName
(OS 10048)Only one usage of each socket address (protocol/network address/port) is normally permitted. :
make_sock: could not bind to address 0.0.0.0:80
No listening sockets available, shutting down
Unable to open logs

It does not write anything in the "error.log". It cannot? why? rights? but it could yesterday! anything changed from yesterday, no nothing!

I have tried to start the server many times today, and it has not written anything in error.log. Looking in the log there are many entries from yesterday, when the server probably worked!?

Okay there most be something using port 80 then!

Output from "netstat -o -n -a | findstr :80" is nothing! netstat says there is nothing listening on port 80.

I'm running SQL Server 2008 Express, and "Reporting Service" would be a prime candidate for listening on port 80, but netstat says it is not!

I'm using the ZoneAlarm firewall (the Apache server has been given full trust and permissions), and it has worked previously, I belive it cannot be the problem.

I'm using Avast anti-virus, but everything is disabled in it, and I'm only using it to run a virus check from time to time.

(I don't think it has anything to do with the "fully qualified domain name", because the setting it is complaining about has always been the same, also when the server is actually working, from time to time)