DVI INPUT= No input signal

Hi,

Monitor turns on with computer then displays DVI input=no input signal and goes dark. Sometimes the monitor will function normally, sometimes it will go dark indescrimately. But the monitor always diplays the DVI INPUT=No input signal at start up, no matter if it functions normally or goes dark. Sometimes turning the monitor off then starting it again solves the problem, but this problem seems to be getting worse as the days go by.

Thanks for helping