Hey'll
All of a sudden
"Windows firewall cannot run because another program or service is running that might use the network translation component ( Ipnat.sys ) " Error when I check my firewall from finding out that my lan users cannot connect to the server anymore ! Windows Server 2003 Small Business

Any idea what caused this & solution ?

Do you have a second software based firewall installed? Did you update one of your security suite softwares like McAfee or Norton from an older version that did not contain a firewall program?

Go to a Command Prompt on the server and type MSCONFIG and hit enter. Look at the Services tab and Startup tab to see if there is anything out of the ordinary.

As a second method of troubleshooting, go to a command prompt and type NETSTAT -A. This will show what ports are in use and also NETSTAT -B will show which ones have active connections and what program is initiating the connection.