and my sony ccfl backlit tv does the same thing. there is a reason for this.
most televisions are either ccfl backlit or backlit by leds around the edge. since they are all tied together and dim or brighten uniformly they alter the output to match the majority of what is on screen.
for instance.. if the scene is bright daylight and you have a black object going across it then that black object will look dark grey since the backlighting is strong. if you have a dark scene with a light object going across it then the light object will be darker than it should be.
if the television did not do this then your dark scene would look dark grey and not black.
now, there might be a way to turn this off, but i haven't figured it out yet. i would like to set the brightness manually and deal with the grey "blacks". if you figure out a lead post it so we can all read into it.
i dont think it has to do with white balance. i think it has to do with an "auto-dimming" or "auto-backlight" or some sort of processing the television does to figure out what backlighting value to set. unless of course the two values correspond somehow.
now... they do make televisions with local dimming backlights which are the tvs with a grid of leds behind the screen which brighten or dim in blocks instead of a complete package. this would reduce the effect as the television would look at each individual block and calculate what backlighting output it should use. i have only seen this on top of the line televisions so far though.