set /etc/ssh/sshd_config KeepAlive 120 but sshd refuses connection

I've installed ESXI 5.0 UPDATE 1 and one of the tuning requirement is to set

KeepAlive 120 in /etc/ssh/sshd_config

However, upon server restart, sshd refuses network connection via putty with port 22.

Please advise.

regards,