Ubuntu latest release 9.10 Karmink Koala using menu "System/Administration/Users and Groups" (french translation)

Select my user
Clic Properties button
Clic "Change Password" button
>>Opens "Change the password" window
Ask me old password : **********
Click "Authenticate" button
System says "Authenticated !"
Enter new password twice : **********
Button "Change the password" can be selected (i.e. the two password are the same)
>>The window "Change the passord" never closes
The button "Change the password" cannont be selected anymore
The button "Close" can be selected
The mouse cursor seems to say "wait... i'm processing"
But after 5 min... nothing

So i decide to clic "Close" Button"

>> users account window comes back with my account
I clic the "Validate" button
This asks me my (old) password to enable this change
The windows closes as if...

But in fact, the password hasn't been changed at all

Please feel free asking me more informations proving a small description on how to give it back.