If it's one of the older LCD monitors with an external power supply you might want to open up the power supply and replace the larger value capacitors. I had this same problem and this cured it.Good luck
u will see the faulty electrolytic- it may have a split case or be leaking and there may be more than one to replace-as nigel said replacements need to be 105 degree hi temp types and be the correct voltage rating as well...........