My LG 37LC55 LCD TV has one half of the screen darker than the other

Sounds like the PSU is on its way out...Faulty Capacitors.

take a look here KIT112 LCD REPAIR KIT LG 37LC55 EAY34796801 EAX32268301 EAX32268301 8

How to fix repair vertical lines on half of LCD tv screen

The CCFL (Cold Cathode Fluroscent Lamp) at the darker end is not lit. Either the CCFL is fused or the ballast is needing repairs.

sonsunny

It can be the auto-contrast is doing its jobs so LG can claim that the TV has really high contrast ratio, also try turning off auto brightness feature off. It gets real bad when the scene has dark back ground such as the dark sky with stars, the TV will really dim down to give real black sky but at the same time you can barely see the stars on the screen, LG is not the only one with this design problem, VIZIO and other has the same problem as well. If you Google your model and search for review you may see that you are not the only one with this problem.
What is the exact model of this TV.
Please let me know what you find.

Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors: http://s807.photobucket.com/albums/yy352/budm
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague

I have had the same problem for a couple of Months . Bought my lg in March 2009, just had it diagnosed as the Screen . Apparently they are not Lg screens but a version called AUO optrix . my tv is a non economical repair and i am waiting for Currys to get back to me . let me know if i can be of any help. Mike my model number is 42LG5010 ZD

This can be fixed easily at a local TV repair shop. I would not recommend trying it yourself as the components that you need to touch carry and electrical charge,

Try clicking the auto adjust button on the screen. If this doesn't work it may be in demo mode, so click the fENGINEbutton on the monitor and make sure it is selected on the normal setting.

The problem is most likley the TV backlight - it is very unlikley to be the graphics card or video input or any other circuitry within the TV.
Also, the problem can be manifested by flashing or flickering of one or both halves of the screen, and sometimes it is a left/right split rather than a top/bottom split, depending on where the lights are positioned. Before failure, you sometimes hear a very high frequency buzz for a few weeks before it fails - the frequency can't be heard by most adults as it ranges from 15kHz-25kHz, but children\animals can usually hear it.
Generally you will need to replace the backlight tube or the invertor that drives it. Generally you can identify the backlights as thin glass tubes buried deep within the panel itself usually with one wire going to each end of them - they are very fragile. The invertor is connected to the backlight tube and looks like a circuit board, often containing a high voltage warning. Usually there are two or four conductors connecting the invertor to the tubes, which can be identified as thicker individual wires as opposed to the flat ribbon wire used for data for the actual image displayed on the screen.
On some screens you may be able to unplug\swap one or both tubes to identify if it's the tube or inverter.

My new TV LCD Samsung LC32C530 Series 5 has one half darker and with less contrast than the other.This is noticeable now always. There is a distinct and clear division down exactly half the display which separates the dark and light sides.. Any ideas?Thank you.

Problems described are related to Backlight.It is possible that backlights of affected area have become weak.
You may need to contact the company for repairs and Yes the Repairs may not be cheap.
Samir