SOLVED!
Man, I spent almost 12hours in front of the bl***y computer!
To make it VERY short:
I had to edit /etc/dolibarr/conf.php
(first, opening a terminal and typing “gksu nautilus” to get rights)
open conf.php with gedit, and editing the path to ADODB.
It stated:
$dolibarr_lib_ADODB_PATH=’/usr/share/php/adodb’;
a search with Nautilus did not show up any php/adodb directories.
So I changed it to what is actually there, in /includes:
$dolibarr_lib_ADODB_PATH=’/usr/share/dolibarr/htdocs/includes/adodbtime’;
which is quite different actually.
What bugs me is, what happened? What was the cause for that?
Anyway, I’m so happy to see my customers, bills and products again! 
Good night!
Jordi
