After restoring the database from the live site to development site, the administrator users fails to log in I want to refresh my DEV site with data from LIVE site.
(both sites have same modules because I play with new modules on my DEV site before I install/enable modules on the LIVE site).

I have set the database configuration to be exactly the same (except localhost for my dev site).
So I dump my database from live site and restore it on my dev site.
(I know I miss some files but I don't care about that.)
All is fine: I can view the dev site with data from the live site, until I try to login as administrator. There is no way to login, no error message; I am simply not logged in.
The password for the administrator user is the same on both the sites, of course.  

I checked the hash of the passwords which are different in table users.
I assumed it was due to some salt, so I also copied the salt from sites/default/settings.php
It does not help: The administrator login is still impossible.
Then I reset the admin password on my dev site as explained in http://drupal.org/node/1023428, but it doesn't help: There is no way to log in.  

What did I miss?
When login fails, you shall get the following error message:


  Sorry, unrecognized username or password. Have you forgotten your password?


You say:


  There is no way to login, no error message; simply I am not logged in.


This suggest that the problem is not with the admin passord, but something else (i.e. your restored site is somehow munged).  In that case, you need to start restoring it from scratch.

Resetting the password will not help if the site is munged, but for the record:

There are several ways to reset the Drupal admin password.  Here they are, sorted from the simplest to use to most difficult:


Request a reset password link sent via e-mail (the most used method).
drush upwd admin --password=&lt;new_password&gt; (as already mentioned by develkar).
./scripts/password-hash.sh &lt;new_password&gt; (as you've found out yourself).


Usually, all of these works.  The shell-script method (#3) is very similar to the drush method (#2), but unlike drush, the shell-script method requires you to insert the generated password hash in the database yourself (using phpMyAdmin or similar tool).