title: Matrix multiplication - "ValueError: matrices are not aligned". Even with same shapes
body: <p>I have two dataframes (exactly the same number of rows and columns). When I perform the following matrix operation: <code>(A).T.dot(Dn).div(Dn.sum())</code>, It works for the first matrix (D1) but for the second(D2), I'm getting the error "ValueError: matrices are not aligned".</p>
  
  <p>D1 and D2 are both dataframes and have exactly the same shape, the same indexes and the same columns. However, the only difference between them is the following:</p>
  
  <p>D1</p>
  
  <pre><code>{dtype('float64'): Index(['10701', '10702', '10703', '10704', '10705', '10706', '10707', '10708',
          '10709', '10710',
          ...
          '32105', '32106', '32107', '32201', '32202', '32203', '32204', '42001',
          '42002', '42003'],
         dtype='object', length=221)}
  </code></pre>
  
  <p>D2</p>
  
  <pre><code>{dtype('int64'): Int64Index([31409], dtype='int64'),
   dtype('float64'): Int64Index([10701, 10702, 10703, 10704, 10705, 10706, 10707, 10708, 10709,
               10710,
               ...
               32105, 32106, 32107, 32201, 32202, 32203, 32204, 42001, 42002,
               42003],
              dtype='int64', length=220)}
  </code></pre>
  
  <p>Any guidance?</p>