When there is some error in uploading any file, Filezilla client retries to upload that file by opening a new connection in addition to the existing connection.
As a result, those connections do not terminate properly and require manual disconnection. Moreover every server will have a limit on the maximum number of simultaneous connections for obvious security reasons.
This can be solved by following steps:
- Login to your cPanel.
- Scroll down the menu until you find FTP Session Control.
- You will see a list of your connections. Click on the button in the DISCONNECT column as long as the status of the connection states IDLE. You might have to click on the DISCONNECT button several times to remove all of the connections.
Disconnect all such IDLE connections and try logging again using FileZilla.
For more information, refer http://www.inmotionhosting.com/support/community-support/file-management/421-too-many-connections-8-from-this-ip
Hope this works.