Display YUV in OpenGL

I think you're addressing U and V values incorrectly. Rather than:

float U = lookupTableU [uvBuffer [ ((y / 2) * (x / 2) + (x/2)) * 2  ] ]; 
float V = lookupTableV [uvBuffer [  ((y / 2) * (x / 2) + (x/2)) * 2 + 1] ];

It should be something along the lines of

float U = lookupTableU [uvBuffer [ ((y / 2) * (YUV_WIDTH / 2) + (x/2)) * 2  ] ]; 
float V = lookupTableV [uvBuffer [  ((y / 2) * (YUV_WIDTH / 2) + (x/2)) * 2 + 1] ];

Next try :) I think you're uv buffer is not interleaved. It looks like the U values come first and then the array of V values. Changing the lines to

unsigned int voffset = YUV_HEIGHT * YUV_WIDTH / 2;
float U = lookupTableU [uvBuffer [ y * (YUV_WIDTH / 2) + x/2] ]; 
float V = lookupTableV [uvBuffer [ voffset + y * (YUV_WIDTH / 2) + x/2] ];

might indicate if this is really the case.