I would first suspect a power supply issue in the monitor, it would require at the least opening the set and looking in the power supply for signs of damage, if its a year or two old look carefully for puffed up caps.
If you are not able to safely get it apart have a tech look at it for you.
In case you do get it open here is what bad filter caps look like, if find that they are fairly easy and inexpensive to replace.
Answers & Comments
I would first suspect a power supply issue in the monitor, it would require at the least opening the set and looking in the power supply for signs of damage, if its a year or two old look carefully for puffed up caps.
If you are not able to safely get it apart have a tech look at it for you.
In case you do get it open here is what bad filter caps look like, if find that they are fairly easy and inexpensive to replace.