Erro ao importar o nltk

Olá, estou com problemas para utilizar o nltk. Quando eu executo a importação do nltk ("import nltk") ele me retorna o seguinte trace:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\site-packages\nltk\__init__.py", line 128, in <module>
    from nltk.chunk import *
  File "C:\Python27\lib\site-packages\nltk\chunk\__init__.py", line 155, in <mod
ule>
    from nltk.data import load
  File "C:\Python27\lib\site-packages\nltk\data.py", line 77, in <module>
    if 'APPENGINE_RUNTIME' not in os.environ and os.path.expanduser('~/') != '~/
':
  File "C:\Python27\lib\ntpath.py", line 310, in expanduser
    return userhome + path[i:]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe3 in position 20: ordinal
 not in range(128)