Just read this article which gives a description on how to archive Twitter stuff with Python. I saw the code and thought 'heck why so complicated?'.

Get python-twitter and do like so:

import twitter

api = twitter.Api()

statuses = api.GetUserTimeline('twitter', count=1000000)
f = open('twitter.txt', 'w')

for s in statuses:
  f.write(s.created_at + '\n' + s.text.encode('utf8') + '\n\n')

This code will get the last million posts of the user twitter and write it to the file twitter.txt in the same directory as the script itself lies in. If your username should not be twitter or if you have more than a million posts you might want to change those values (and in the latter case consider getting professional help).