cam.Start2D() -- Looks http://wiki.garrysmod.com/page/cam/Start2D for info about that

hook.Add( "HUDPaint", "HUDPaint_DrawABox", function()
    draw.RoundedBox( 30, 1300, 20, 350, 200, Color( 0, 0, 0, 100 ) ) -- Draw a box
end )

draw.SimpleText( "VIE", "Default", 30, 30, Color( 0, 0, 0, 255 ), 1, 1 ) -- The string "Life" don't appears

cam.End2D()