Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Install and Configure FileZilla on Mac OS
FileZilla is a popular free FTP desktop client compatible with Mac OS X 10.5 and later versions. To install and configure it on your Mac, do the following.
1) Download FileZilla to your Mac from the app’s official website. Make sure you’ve chosen your processor type – either Intel or PowerPC. If not sure, select Intel, as it is used by newer Macs.
2) Run the installation package. If you use Safari as your browser, the package contents will be automatically extracted. Double-click the extracted file to start the installation. First of all you should accept FileZilla’s license agreement and select a location for your FileZilla files. Having completed other common installation steps, click Install.
3) Specify details for logging in to your FTP account:
• FTP server name: Name of the domain or FTP server that hosts your account
• FTP username: cPanel username
• FTP password: cPanel password
• Mode: passive
4) Click the Quickconnect button in the FileZilla toolbar to nonnect to your FTP account. If the connection is successful, you’ll see a note in the status area at the top of the screen. Files and folders belonging to your web hosting account will be present in the Remote Site pane on the right, whereas your Mac’s files and folders will be shown in the Local Site pane on the left. Use the drag-and-drop feature to transfer files and folders between your local computer and your hosting account.