I commented out nearly all code now. Only these are executed:
Code:
in formCreate:
  nx.CreateGlWindow(self);

in onTimer:
  if cube=nil then begin
    // Do glCheckFramebufferStatus
    if not nx.CanRender then exit;

    err:=glGetError();
    if err>0 then ShowMessage(format('Model_before: glGetError, code: %d',[err]));

    model:=TGLModel.Create;
    model.LoadFromW3D('cube.w3d');
    model.UseMaterials:=false;
    model.MakeDisplayList(cube);
    model.Free;

    err:=glGetError();
    if err>0 then ShowMessage(format('Model_after: glGetError, code: %d',[err]));
    // Seen code 1286 (GL_INVALID_FRAMEBUFFER_OPERATION)

    exit;
  end;
I get only 1 messagedialog with "Model_after...1286".

So FBO is not being used at all, just rendering vertex array to displaylist. If i comment out "model.MakeDisplayList(cube);", then no error comes.

I also made a guide in the nxPascal wiki to show how to easily install the SVN version. It shouldn't take more than 1 minute if you already have SVN environment in your system, something like TortoiseSVN, or linux comparative. This whole demo is included there.