Render Texture doesn't work properly runtime

Hello Everyone! I'm having a little issue about render texture.. i basically did an ngui menu projected on a plane in front of the character,but it could be everything, a video or a webcam signal, what i don't get is when i compile my exe, the render texture works only on lower resolution, 800x600 maximum, if i go one step further, everything that was rendered on my plane, disappear.. how's that possible? even in unity-runtime works perfectly.. Any ideas? thank so much!!