BUG: odd indexing issue w.r.t series/frame div op (may involve numexpr)

worked in 0.13.1

works for n = 4, but not 4000

```
        for n in [ 4, 4000 ]:

            df = DataFrame(1,index=range(n),columns=list('abcd'))
            df.iloc[0] = 2

            expected = DataFrame(np.tile(df.mean().values,n).reshape(n,-1),
                                 columns=list('abcd'))/df
            result = df.mean()/df
            assert_frame_equal(result,expected)
```
