I had the same problem with the 770, and then again with the n800. The solution worked for the n800, so I'm assuming this solution will also work for the 770.

1. Go into Application Manager->Tools->Application catalog->extras->details

2. Right now the web address (URL) should read "http://repository.maemo.org/extras"

3. Change the URL to "http://repository.maemo.org/"

This worked for Maemo Mapper as well as Python. Good luck to ya.