Hi again,
first of all, thanks for the answer.
i checked the state and they are OK.
i checked the opengl Errors and gives "invalid operation" on glBindFramebuffer(GL_FRAMEBUFFER, mFrameBufferId);. It seems that the FBO ID becomes invalid after the change of the video mode.
also, i checked GDebugger and indeed... the FBOs of previous context still there.
so i don't have any more clues.
i dont know if you have another ideas.
note: im using SFML 2.0 only for the OpenGL window creation.