I have a LG 42LD 550 just got it, couple day, it began turning itself on & off, the LG start up screen comes on, its not responding to the remote or the switches on the TV, any idea what is the problem??

If you only have it since a couple of days, don't mess with it. Claim your warranty; get it changed, it is a vey Bad Buy. If they don't want to change it, at least get it repaired as soon as possible

If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/
Faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent.
Type in the brand name of your device, in the search box [at the top right] of the display window and the Search will start at once as you type in, and will show you all the related posts. It will make surf easy.

sounds like bad power supply

try pressing the minus key multiple times firmly.It should respond.
The switches need to be replaced.
Samir

My Phone has done that a couple of times before. It would slowly start turning off more & more often then it wouldn't turn on with the same problem as you.

Turns out it was the battery as it was a couple of Months old & was out of warranty.

Furst, check the video signal cable, if you can, try a replacement. Try removing and then refitting the original, sometimes this clesans the connections

I have the same problem. But i had solved it. I use a lighter to burn on my viewty's touch screen, and it is working properly again within 30 secs. And ofcourse, do not burn the touch screen without a screen protector. Hope this solution would help.

Well, I have 2 of these monitors and one began acting in a similar fashion right before the cable went bad. I acquired a replacement from another person with a broken monitor but I believe this site sells them too (but they aren't cheap).

http://servicesales.sel.sony.com/ecom/accessories/web/productSearch.do?searchOperation=modelSearch&searchText=SDMN80

Sounds like the machine has been wet/moist have you tried drying it in a sealed bag with several silica gel bags for a couple of days?