It does look like your pycrypto install hasn't worked.
I'm afraid I have 10.6 and the structure is slightly different than 10.5, I have
Computers Hard Drive, Library, Python, 2.6, site-packages, Crypto
I did have a similar problem when I tried installing initially, I unzipped the pycrypto package but didn't use all the directories. eg:
When I unzipped it I ended up with:
pycrypto2.0.1, pycrypto2.0.1 and then the files.
I then moved all the files up a level before trying to install pycrypto and it didn't work. Re-created the structure as it unzipped and re-ran the installer and it then worked.
If you can't get the test file to run, it hasn't been installed correctly. Which isn't much help I'm afraid.
Your:
[iMac:~] eric% python2.6 /Users/eric/Desktop/ineptepub.py
is correct in its usage (at least it works for me) but not having 10.5 I cannot remember what I used to have.