nltk.download() hangs on OS X

nltk.download() is hanging for me on OS X. Here is what happens:

$python
>>> Python 2.7.2 (default, Oct 11 2012, 20:14:37) 
>>> [GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
>>> import nltk
>>> nltk.download()

showing info http://nltk.github.com/nltk_data/

After that, it completely freezes.

I installed everything according to the ntlk install page. I'm on OS X 10.8.3. On my Linux box, it just works with no problems.

Any ideas?