Downgrading modem firmware and repairing it
OS X users
visit this tutorial next.
Start at Step 3, and specifically, at this line "Click the "SSH" tab and click the "Install SSH/SFTP/SCP" button."
Follow this tutorial all the way to the end.
Windows users
visit this tutorial next.
Start at Step 4. Skip Step 5. Continue at Step 6, then follow the tutorial all the way to the end.