Unexpected result/segmentation fault with .ix/.loc (0.12.0)
Hitting a seg fault on a specific usage of .ix/.loc with release 0.12.0 (and current master).  Any help is greatly appreciated.  Let me know if I can provide any more info.

Here's an example produced with pandas 0.12.0 and numpy 1.7.1.

```
>>> df = pd.DataFrame({"A": [0, 1, 2]})
>>> print df.ix[[0,8,0]]  # unexpected results
              A
0  0.000000e+00
8           NaN
0  4.677219e+12
>>> df = pd.DataFrame({"A": list('abc')})
>>> print df.ix[[0,8,0]]
Segmentation fault (core dumped)
```

(.loc in place of .ix fails in the same way)

For comparison, here's the behavior with 0.11.0:

```
>>> df = pd.DataFrame({"A": [0, 1, 2]})
>>> print df.ix[[0,8,0]]
    A
0   0
8 NaN
0   0
>>> df = pd.DataFrame({"A": list('abc')})
>>> print df.ix[[0,8,0]]
     A
0    a
8  NaN
0    a
```

System info

```
i686 GNU/Linux
```

Python info

```
Python 2.7.3 (default, Apr 10 2013, 05:09:49) 
[GCC 4.7.2] on linux2
```
