Failure to write large dataframe to file: "SystemError: error return without exception set"
I have a simple but large dataframe. I can write it to disk using .to_csv(). The file size is then 11GB. It looks like this:

```
TLID2,NEAR_DIST,TLID1,TLID2,yr1,yr2,yr2_older
104519610,487,104519631,104519610,1952.0,1912.0,True
104519610,418,104519632,104519610,,1912.0,False
104519610,747,104519451,104519610,,1912.0,False
104519610,559,104519645,104519610,,1912.0,False
104519610,979,104582619,104519610,,1912.0,False
 ...
```

But when I use DataFrame.save(), it fails after 1.9GB with a strange error:

```
    548     prox_table.to_csv(output_path+'proxim_table_all.csv')
--> 549     prox_table.save(output_path+'proxim_table_all.pandas')
    550 

lib64/python/pandas-0.11.0-py2.6-linux-x86_64.egg/pandas/core/generic.pyc in save(self, path)
     26 
     27     def save(self, path):
---> 28         com.save(self, path)
     29 
     30     @classmethod

lib64/python/pandas-0.11.0-py2.6-linux-x86_64.egg/pandas/core/common.pyc in save(obj, path)
   1562     f = open(path, 'wb')
   1563     try:
-> 1564         pickle.dump(obj, f, protocol=pickle.HIGHEST_PROTOCOL)
   1565     finally:
   1566         f.close()

SystemError: error return without exception set
> /lib64/python/pandas-0.11.0-py2.6-linux-x86_64.egg/pandas/core/common.py(1566)save()
   1565     finally:
-> 1566         f.close()
   1567 
```

The df looks like:

```
ipdb> prox_table.dtypes
NEAR_DIST      int16
TLID1          int64
TLID2          int64
yr1          float16
yr2          float16
yr2_older       bool
dtype: object
ipdb> prox_table
<class 'pandas.core.frame.DataFrame'>
Int64Index: 246425908 entries, 104519610 to 21973121
Columns: 6 entries, NEAR_DIST to yr2_older
dtypes: bool(1), float16(2), int16(1), int64(2)
```

I'm using pandas v 0.11.0. The machine is running  RHEL 6.1 and has 384GB of RAM and plenty of disk space.
