DLP670S: Problem setting DMD Idle Mode

We are trying to enable DMD Idle Mode on a DLP670S.  On the target system we have verified that this works using the DLPC900REF-GUI.

Below is the code which is heavily based on the DLPC900REF-GUI\Source.  The code below results with the following error:

"Could not set DMD Idle mode. Error: \"Unknown error\""

Here is the code:

bool DLPC900ProjectorV2::SetIdleMode(bool on)
{
int SLmode = 0;

int SLmode = 0;
if (DLPC900_GetMode(&SLmode) == 0)
{
  if (!SLmode) //this is not supported in video mode
  {
    QString err = GetError();
    if (err.isEmpty())
      qDebug() << STR("Error: SetIdleMode not supported in Video Mode.");
    else
      qDebug() << STR("Error: SetIdleMode not supported in Video Mode. Error: %1") << err;
return false;
}
}

if (DLPC900_SetMode(VIDEO_PATTERN_MODE) < 0)
{
qDebug() << STR("Could not set video pattern mode");
return false;
}

// if sequence is already running., it must be stopped before configuring patterns
if (DLPC900_PatternDisplay(STOP_PATTERN_DISPLAY_SEQUENCE) < 0)
{
  qDebug() << STR("Could not stop pattern display sequence. Error:%1") << GetError();
  return false;
}

if (DLPC900_SetDmdIdleMode(on) < 0)
{
  QString err = GetError();
  qDebug() << STR("Could not set DMD Idle mode. Error: %1") << err;
  return false;
}

}