DataFrame fail if columns is non-unique MultiIndex
In [33]: cols2 = pd.MultiIndex.from_tuples(list(itertools.product(['A', 'B', 'C'], ['X', 'Y', 'Z']))*2)

In [34]: df2 = DataFrame(np.random.randn(3, len(cols2)), columns=cols2)

In [35]: df2
Out[35]: ---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-35-d4a59695a920> in <module>()
----> 1 df2

/Users/changshe/code/ipython/IPython/core/displayhook.pyc in **call**(self, result)
    236             self.start_displayhook()
    237             self.write_output_prompt()
--> 238             format_dict = self.compute_format_data(result)
    239             self.write_format_data(format_dict)
    240             self.update_user_ns(result)

...

/Users/changshe/code/pandas/pandas/core/format.pyc in _get_formatted_column_labels(self)
    341             fmt_columns = self.columns.format(sparsify=False, adjoin=False)
    342             fmt_columns = zip(_fmt_columns)
--> 343             dtypes = self.frame.dtypes.values
    344             need_leadsp = dict(zip(fmt_columns, map(is_numeric_dtype, dtypes)))
    345             str_columns = zip(_[[' ' + y

/Users/changshe/code/pandas/pandas/core/frame.pyc in **getattr**(self, name)
   1764             return self[name]
   1765         raise AttributeError("'%s' object has no attribute '%s'" %
-> 1766                              (type(self).**name**, name))
   1767 
   1768     def **setattr**(self, name, value):

AttributeError: 'DataFrame' object has no attribute 'dtypes'
