User password update

Hi Kriesi team!
I have a weird situation!
I built an ‘update your profile’ form that successfully updates users profile for all attributes (first name, last name, email address, …) except one: password :(
If the password field is filled by the user, it updates the password if not, the existing password is kept. So far so good.
However, only when the password field is filled, once the page refreshes with confirmation message and all, I get a 500 Internal Server Error on whatever link I click. If you close by browser and then re-open it, all is back to normal.
Is this related to Enfold? Any idea where I should search?
FYI, my script is simply:
if($rep_pwd != “”){
wp_set_password($user_pwd,$user_id);
}
(I made sure that user_pwd & $user_id are OK, they echo nicely when asked)
Thanks!!!