windows build test failures
getting test failures on the windows builds. this is from py27 64-bit:

```
======================================================================
ERROR: test_replace_convert (pandas.tests.test_frame.TestDataFrame)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\workspace\pandas-windows-test64-py27\pandas\tests\test_frame.py", line 6869, in test_replace_convert
    assert_series_equal(expec, res)
  File "C:\workspace\pandas-windows-test64-py27\pandas\util\testing.py", line 197, in assert_series_equal
    assert_almost_equal(left.values, right.values, check_less_precise)
  File "C:\workspace\pandas-windows-test64-py27\pandas\util\testing.py", line 141, in assert_almost_equal
    assert_almost_equal(a[i], b[i], check_less_precise)
  File "C:\workspace\pandas-windows-test64-py27\pandas\util\testing.py", line 146, in assert_almost_equal
    if isnull(a):
  File "C:\workspace\pandas-windows-test64-py27\pandas\core\common.py", line 60, in isnull
    return _isnull(obj)
  File "C:\workspace\pandas-windows-test64-py27\pandas\core\common.py", line 74, in _isnull_new
    return _isnull_ndarraylike(obj)
  File "C:\workspace\pandas-windows-test64-py27\pandas\core\common.py", line 135, in _isnull_ndarraylike
    values = np.asarray(obj)
  File "c:\python27\lib\site-packages\numpy\core\numeric.py", line 235, in asarray
    return array(a, dtype, copy=False, order=order)
ValueError: invalid __array_struct__

======================================================================
FAIL: test_insert_column_bug_4032 (pandas.tests.test_frame.TestDataFrame)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\workspace\pandas-windows-test64-py27\pandas\tests\test_frame.py", line 10084, in test_insert_column_bug_4032
    assert_frame_equal(result,expected)
  File "C:\workspace\pandas-windows-test64-py27\pandas\util\testing.py", line 238, in assert_frame_equal
    check_less_precise=check_less_precise)
  File "C:\workspace\pandas-windows-test64-py27\pandas\util\testing.py", line 199, in assert_series_equal
    assert(left.dtype == right.dtype)
AssertionError
```
