RandomPool instance has no attribute '__len__'

Greetings, 

I trying to run the "Crypto.PublicKey: Public Key Algorithms" example from 
pycrypt (under Python 2.5.1)

http://www.amk.ca/python/writing/pycrypt/ 

Here'y my code:

=== Begin RSATest.py ===
1) from Crypto.Cipher import *
2) from Crypto.Util import randpool
3) from Crypto.Hash import MD5
4) from Crypto.PublicKey import RSA
5)
6) class RSATest():
7)    
8)    def foo(self):
9)        
10)        plaintext = "this is some text"
11)        RSAkey=RSA.generate(384, randpool.RandomPool)
12)        hash=MD5.new(plaintext).digest()
13)        signature=RSAkey.sign(hash, "")    
14)        print RSAkey.verify(hash, signature)     # will check out    
15)        print RSAkey.verify(hash[:-1], signature)# will fail
16)
17)__name__ == "__main__":
18) d = RSATest()
19)d.foo()
=== End RSATest.py ===

I'm getting the following error when entering line 19 above:
AttributeError: RandomPool instance has no attribute '__len__'

Here's the stack trace:

=== Start trace ===
(...)
RSAkey=RSA.generate(384, randpool.RandomPool)
  File "D:\Python25\Lib\site-packages\Crypto\PublicKey\RSA.py", line 40, 
in generate
    p = pubkey.getPrime(bits/2, randfunc)
  File "D:\Python25\lib\site-packages\Crypto\Util\number.py", line 89, in 
getPrime
    number=getRandomNumber(N, randfunc) | 1
  File "D:\Python25\lib\site-packages\Crypto\Util\number.py", line 53, in 
getRandomNumber
    value = bytes_to_long(S)
  File "D:\Python25\lib\site-packages\Crypto\Util\number.py", line 185, in 
bytes_to_long
    length = len(s)
AttributeError: RandomPool instance has no attribute '__len__'
=== End trace ===

The error is raised in bytes_to_long() in number.py. 

Did anybody else run into this problem? What am I doing wrong here?

Any help is much appreciated.

--Alex