type
  TMyData = record
    Group: Integer;
    Name: String[100];        // Works
    Description: String[255]; // Fails
    Tag: Boolean;
  end;
  PMyData = ^TMyData;

...

  ihObj:= ievFront.AddNewObject;
  ievFront.ObjKind[ihObj]:= iekPOLYLINE;
  ievFront.ObjBrushStyle[ihobj]:= bsSolid;
  ievFront.ObjBrushColor[ihobj]:= clRed;
  ievFront.ObjPenWidth[ihObj]:= 1;
  ievFront.ObjPenColor[ihObj]:= clBlack;
  ievFront.ObjStyle[ihObj]:= [ievsVisible, ievsSelectable, ievsSizeable];
  ievFront.OffScreenPaint:= True;
  ievFront.PolylineClosingMode:= iecmAlways;
  ievFront.SetObjPolylinePoints(ihObj, MyPointsArray);
  ievFront.ObjPolylineClosed[ihObj]:= True;
  GetMem(MyData, SizeOf(TMyData)); 
  MyData^.Group:= 0;
  MyData^.Name:= IntToStr(ihObj)+#0;        // Tried With and Without #0
  MyData^.Description:= 'Does Not Work'+#0; // Tried With and Without #0
  ievFront.ObjUserData[ihObj]:= MyData;
  ievFront.ObjUserDataLength[ihObj]:= SizeOf(TMyData);
  // If I free here (FreeMem(MyData, SizeOf(TMyData));) we get errors

...

procedure TfMain.ievFrontObjectOver(Sender: TObject; hobj: Integer);
var
  s: String;
begin
  StatusBar1.Panels[1].Text:= '';
  if hobj = 152  then begin
    s:= 'debug';
  end;
  try
    MyFetchData:= ievFront.ObjUserData[hobj]; 
    if MyFetchData <> nil then begin
      // Description Always is '' // Tried MyFetchData^.Description too
      StatusBar1.Panels[1].Text:= MyFetchData.Description; 
    end;
  except
  end;
end;