crashes, when "rankdir=LR" is specified for the following graph...
Input:

digraph D {
  ratio=0.75;
  concentrate=true;
  node[fontname=Arial, fillcolor="#8591D3", style=filled];
  rankdir=LR;  # if uncommented dot runs without error
  subgraph cluster0 {
    label = "DAAC";
    style = filled;
    color = "#8591D3";
    node [style=filled, fillcolor=white];
    daacHwIfTestAnalog2Rxde;
    daacHwIfTestSusa2Lasu;
    daacHwIfTestDiscreteLoop;
    daacHwIfTestSusa2Analog;
    daacHwIfTestCpa2Lasu;
    daacHwIfTestRxde2Txde;
    daacHwIfTestSusa2Discrete;
    daacHwIfTestAnalogLoop;
    daacHwIfTestLasu2Cpa;
    daacHwIfTestTxde2Rxde;
    daacHwIfTestModeGet;
    daacHwIfTestAllowed;
    daacHwIfTest;
  }
  pus8Tc1Proc -> daacHwIfTest [label="P"];
  daacHwIfTest -> daacHwIfTestAnalog2Rxde;
  daacHwIfTest -> daacHwIfTestSusa2Lasu;
  daacHwIfTest -> daacHwIfTestDiscreteLoop;
  daacHwIfTest -> daacHwIfTestSusa2Analog;
  daacHwIfTest -> daacHwIfTestCpa2Lasu;
  daacHwIfTest -> daacHwIfTestRxde2Txde;
  daacHwIfTest -> daacHwIfTestSusa2Discrete;
  daacHwIfTest -> daacHwIfTestAnalogLoop;
  daacHwIfTest -> daacHwIfTestLasu2Cpa;
  daacHwIfTest -> daacHwIfTestTxde2Rxde;
  daacHwIfTest -> daacHwIfTestModeGet;
  daacHwIfTest -> daacHwIfTestAllowed;
  daacHwIfTest -> errClear;
}