can't obtain items from DatetimeIndex'ed DataFrame
found that my numpy-vbench setup was not working for a while due to need for fresh cython... upgraded cython.  Now I am trying to render pages where I got code hitting https://github.com/pydata/pandas/issues/4547  but even rebuilding pandas current master ( v0.14.0rc1-51-gccd593f) using cython 0.19.2+git5-g0c6fdf0-1~nd70+1 resulted in the same failure, so I decided to change my code but got stuck with inability to reference entries in the DataFrame using its own index items:

This session is with prev release:

```
(Pdb) print pandas.__version__
0.13.1
(Pdb) print means[means.index[0]]  # works for this one
0.000877753633415
(Pdb) print results[results.index[0]] # but doesn't for another one with the same index
*** KeyError: u'no item named 2011-03-13 11:39:17'
(Pdb) print np.all(results.index == means.index)
True
(Pdb) print results.index
<class 'pandas.tseries.index.DatetimeIndex'>
[2011-03-13 11:39:17, ..., 2014-05-19 13:35:52]
Length: 1735, Freq: None, Timezone: None
(Pdb) print results
                    revision ncalls    timing traceback
timestamp
2011-03-13 11:39:17  c3f4e89  43690  0.000868      None
2011-03-14 00:44:47  c5c3cb9  43690  0.000855      None
(Pdb) print (results.index == results.index[0])[:2] # clearly item is there
[ True False]
```

in current master it was similar:

```
(Pdb) print pandas.__version__
0.14.0rc1-51-gccd593f
(Pdb) print (results.index == results.index[0])[:2] # clearly item is there
[ True False]
(Pdb) print results[results.index[0]]
*** KeyError: Timestamp('2011-03-13 11:39:17')
```

am I doing something stupid or there is a bug somewhere?  didn't look into how those timestamps stored in the sqlite DB and brought back -- may be loading/unpickling? them back somehow causes this behavior... just awkward
