Symptoms: Unable to connect with or even see servers.
Cause: Your firewall blocks incoming and/or outcoming connections for Freelancer.
Solution(s): Firewalls are numerous and each have their own method for unblocking programs. It is best to look in your firewall's help for instructions on how to unblock a program. If you do not believe you have any firewall installed, you may still be using Windows Firewall, which is built in Windows XP starting from Service Pack 2 and above.
To add a program to the exceptions list in the Windows Firewall, open up your Control Panel (which can be found under My Computer or in the Start Menu usually). Look for either a Security Center or a Windows Firewall icon. In the Security Center (if applicable), select the Windows Firewall link toward the bottom of the window. Both methods will open up the main Windows Firewall window.
If using Windows XP: in the "Exceptions" tab, hit "Add Program...". If on Windows Vista or 7, look for "Allow a program or feature through Windows Firewall" on the left menu. Then, you may need to click on "Change settings", after which you will be allowed to click on "Allow another program...".
In the dialog box that appeared, hit "Browse..." and reach Freelancer's executable (which, by default, is located in C:\Program Files\Microsoft Games\Freelancer\EXE\). Hit OK twice and you should be good to go!