[Plugin: NextGEN Gallery] nextgen can write file but nothing in database

when I create a new galerie or upload new images : nextgen can write on disk but nothing is saved in database.

I verified my db_user & privileges.
I don’t have any error message.
when I create post or article all works fine.

this happen on a wordpress I didn’t install myself but I have to care and upgrade it.
nothing seems to be wrong. On the same server, many WP and nextgen are installed and none else has problem. I tried to compare files… i found nothing wrong….

I don’t know where to look for…. does someone has an idea ?
does someone have the same problem ?

thanks, toma

http://wordpress.org/extend/plugins/nextgen-gallery/