should be dumb as everybody seems to installed it without trouble.
I spent hours within a fresh squeeze and tried different configurations (easy_install, aptitude and from source 0.81p.tar.gz) the best I got is a page from the localhost:9989 
without any slave started.
Knowing that I made the 2 accounts : buildmaster and buildslave 
how to clean and reinstall it to have server and 1 slave for git ?
thanks in advance

Added :
You are right some details are missing:
I use buildbot from virtualBox with a Debian squeeze 6.0 in 32bits
The both accounts : buildmaster and buildslave are running within this same Virtual environment.
I just tried the little example (this seems really interesting) :
easy_install buildbot
buildbot create-master /tmp/experimental_buildmaster
buildbot start /tmp/experimental_buildmaster

as root the jinja2 was missing whereas from buildmaster there were no complain (??)
commented the Git calls that created errors to try to start the simplest demo
buildslave create-slave /tmp/experimental_buildslave 127.0.0.1:9989 slave-name mypasswd
in the log something appear allways : "No address associated with hostname"

it seems I'm closer with this no ?
Some additional information about configuring abd running buildslave after it's creation.
After installing buildbot package int.d script /etc/init.d/buildbot is added to enable running buildbot as a service (starting automatically after system restart and so on).
For this script to run successfully you need to edit conf file for this script. File name is specified inside the script, typically it is /etc/default/buildbot. Options in this file are pretty clear. One interesting thing you can tune here - the user from which buildbot will be running (default is buildbot). Small example of when it is useful:
I had to write a buildbot task, one part of which was managing virtual machines running on builslave machine (starting, stopping, managing snapshots). But rights for doing this had only vbox user (I used Virtual Box VMs). So I simply changed the user field in /etc/buildbot/default to accomplish this.
I hope this information will be useful to you.
buildbot from start