Monitor not waking up from Power Save mode

[mahesh]

I have an older version of Ubuntu (11.x). After a long period of not using, I turned on my Ubuntu Desktop. It loaded all the way to the login screen. Eventually the Monitor went into sleep mode and I am unable to "wake up" the system. I have clicked on the keyboard and mouse many times but the Monitor does not wake up. The Desktop is running.

I turned the monitor ON/OFF, it says, going into Sleep mode and does not respond.

How to fix this ?

Tks
Syed
.ps Previously all was working but I had not logged in for a long long time. Trying to get back to Ubuntu.