I’ve found my problem :
1) There was a difference between my two database. The first was UTF-8 Unicode (utf8) and latin1_leneral_ci, but the second was UTF-8 Unicode (utf8) and utf8_bin.
2) When I’ve imported the data from the first base to the second the character of the sql file was set to utf8 instead of latin1.
So I did the following :
Set my second database to UTF-8 Unicode (utf8) and latin1_leneral_ci.
Choose latin1 character set during the backup importation on the second base.
If you ve yhe same error take a look on the character paramters of your new database, and you’ll find the solution.
Hope it’ll help somebody.
Luffy.
(WORDPRESS 2.5)