You can't toggle display on <option> elements in Safari (or IE, for that matter). This is part of a long and inconsistent tradition with Safari restricting CSS styling functionality on form elements, believing the visual language of interactive elements should be consistent with the OS (no point trying to find a rationale for IE's failings).
Your only options are either to remove it (and re-append it later), or to set it to optnz.disabled = true. Sorry for the bad news!
