.loc function failed
env: windows 7 64bit, pandas 0.12 

``` python
In [106]: res
Out[106]:
<class 'pandas.core.frame.DataFrame'>
Int64Index: 93705 entries, 13 to 93713
Columns: 3561 entries, 2) to 3561)
dtypes: float64(3561)


In [107]: res.loc[12]
Out[107]:
0
2)     3.362026
3)     1.574658
4)     1.905283
6)     2.069734
8)     4.777519
9)     4.316618
11)    2.231455
......
```

my res's index starts with 13, but the numeric index loc[12] has values.  
