Error 400 Bad Request

wooa

hi,
i have just installed zenphoto-1.2.3 in french version , but when i want to edit and save admin aoptions
(zp-core/admin-options.php?action=saveoptions)

i have this message :

"Bad Request
Your browser sent a request that this server could not understand."

Do you know what to do to correct this ?
Maybe it is due to utf8..i am working to find the solution, and i didn't find it yet.

thanks in advance for your help

Stella