This trail isn't about the frame buffer. Frame buffer trails are related to translation or rotation (movement in general) because the last frame is always kept. This trails is because I'm drawing a region of the sprite that has 'nothing' on it. I think when I call the method, opengl just replicates the last row of pixels. Anyway, the problem is solved. Using trickery but still... solved.
KOP - Kludge Oriented Programming.