When the code in .../user/edit.php (and editadvanced.php) encounters an error trying to update the user details in the external authentication system, it displays an error using the value of $usernew->auth, which sometimes is not defined (e.g., when the user itself is editing his/her own profile). In addtition to that, the code actually tries to update the profile in the authentication system indicated by $user->auth (see line 69 in edit.php, where the call to get_auth_plugin is made()).

So we should be really using $user->auth for the error message.

I'm attaching a couple of patches for both 1.8 and 1.9dev, to fix this.

Saludos. Iñaki.