I was playing with my Raspberry PI with Raspbian and the ssh connection was dropping (or timeouting, or something like this), I got a "Broken Pipe" message, and If I tried to connect again, it refuses it.
I don't know why, but to fix it edit /etc/ssh/sshd_config with
sudo nano /etc/ssh/sshd_config
Search for TCPKeepAlive and update it from yes to no
It doesn't make sense, I know, but it worked.
No mínimo estranho pois deveria melhorar ativando o keepalive e não ao contrário.