Hi @tizz & @photocrati,
I’ve checked the website for any malware, nothing wrong to me 🙁
I’ve set the theme to the wordpress default one, nothing changed.
I desactivated all the other extensions, nothing changed.
BUT, I did not try this earlier (sorry), I updated every gallery (without any modification), I deleted my album, recreated it with the same gallery.
Every thing is working fine now.
Any known bug about broken links after upgrading nextgen?
Thanks both of you for your help, thanks photocrati for the nextgen extension 😉