Monitor Flickers on and off

I have a Dell ST2310 monitor that I used for about a year.  When moving the monitor to another PC, when the power cord is attached the screen flashes on/off/on/off continuously.  I can briefly see the Dell logo on a black screen during the flashing.  I tried using two additional power cords and hooking it up to a 3rd pc but have the same results.  The monitor worked fine when I used it last (about 2 months ago.  What is causing the flashing and how do I fix it?

Any insight would be much appreciated. 

Thank you.