JQuery Form Plugin ajaxForm() Missing & Vars For input type="image"

Question

I'm having problem getting the ajaxForm() function of JQuery Form Plugin 2.24 (with JQuery 1.2.6) to work with <input type="image">

For the first time, it does POST correctly, e.g., """&vu.x=13&vu.y=7""" (among other vars) and updates the designated portion within the outer <form>...</form> with the AJAX response, everything seems to be fine.

However, the """&""" vars are completely missing from the subsequent AJAX POSTs.

I try to set "semantic: True" according to its documentation, but to no avail.

It probably still sounds hopelessly confusing -- the live problem is with the link vote up/down portion of the site CollectiveSys (sorry registration/login is required to vote).

Many thanks in advance.