Can't access MySQL after sourcing a database and reboot
Oh, you nailed it!

It seems that my dump actually contained mysql.user data, so that after loading the database, I could only connect with these distant login information.
Taking a look at this mysql.user table, it appears that these login were specified, not for localhost, but the distant host.

Anyway... Knowing this, I've  been able to connect to mysql client, then reset these login info :

mysql –u root –p [distant password]
use mysql.user UPDATE mysql.user
SET Password=PASSWORD('MyNewPass') WHERE User='root';
FLUSH PRIVILEGES;
quit


I finally deleted these distant host lines from phpmyadmin, to be sure not to mess anything up.

Thanks a lot for your help !