monitor problem

My Dell E176FP monitor just started acting wierd.  When it is plugged in, but the computer is off, it cycles continously through various colors (full screen) and does not respond to the power or menu buttons.  While in this condition, as the computer starts up a message "auto adjust in progress" displays briefly while the Windows screens come up.  While the computer is on, everything is normal, and the monitor responds as it should to the power and menu buttons.  But then after the computer is shut down, the monitor acts wierd as described above.  I have been using this computer and monitor without problems for about 15 months.  I have not done anything different to cause this problem which just arose.

 

When wierd, it makes no difference if the monitor cable is connected to the computer.  Holding down the menu button for 15 seconds makes no difference.