Comodo Internet Security is a freeware software package for Windows that that controls the programs that can connect to the outside world and the types of connections that they can make. If the Comodo Firewall component isn't configured correctly, it can prevent Firefox from accessing the Internet, causing Firefox to give Server not found errors.
This article describes how to configure Comodo Internet Security to allow Firefox access to the Internet.
Open Comodo Internet Security - click the Windows Start button, then select All Programs > COMODO > COMODO Internet Security > COMODO Internet Security.
At the top of the COMODO Internet Security window click the Firewall icon to open the Firewall panel.
On the left side of the Firewall Panel, under Firewall Tasks, click the Advanced icon.
Click on the Network Security Policy link in the Firewall panel to open the Network Security Policy window.
In the list, look for Firefox or firefox.exe and then click on its name to select it.
Click Remove. The entry for Firefox will disappear.
Click Add.... The Application Network Access Control window will appear.
Next to the Application Path: field, click Select, and then click on Browse....
Navigate to the Firefox installation folder (e.g. C:\Program Files\Mozilla Firefox\) and double click on firefox (firefox.exe).
In the Network Access Rules section, select Use a Predefined Policy, and in the dropdown select Web Browser.
Click Apply to close the Application Network Access Control window.
Click the X in the top-right corner of the COMODO Internet Security window to close it.