bug or unhelpful error message in 0.12 and trunk: IndexError: Out of bounds on buffer access (axis 0)
The following raises the error

```
pandas.Series([0.1, 0.2], index=[1, 2]).loc[[2, 3, 2]]
```

whilst

```
pandas.Series([0.1, 0.2], index=[1, 2]).loc[[2, 2, 3]]
```

does not. Or is there something invalid with this code?
