Symptoms: Unable to connect with or even see servers.
Cause: Windows Vista may be not updated to Service Pack 2 or above.
Solution(s): The only thing to do is to make sure Windows is fully updated! Open up your Control Panel (which can be found under My Computer or in the Start Menu usually) and look for the Windows Update icon. In the left menu, hit "Check for updates" and wait for Windows to find all available updates. If any updates are found, click "View available updates". In the list, deselect any update you do not want and install the rest. Repeat this process as many times as necessary for Windows Update not to give back any update to install.
Notice: This technical issue does not apply to Windows 7, which already has the updates implemented by the SP2 built-in.