"Argument not an array" on some Uploads

We're experiencing a problem where the upload fails with a message from Drupal "An illegal choice has been detected. Please contact the
site administrator."

The error logs return:

Type: php
array_merge() [function.array-merge]: Argument #2 is not an array in /home/loktah/public_html/sites/all/modules/drupal-modules/filefield/filefield_widget.inc on line 255.
Backtrace:
array_merge(array)[filefield_widget.inc:255];
.filefield_widget_value(array)[form.inc:1024];
.._form_builder_handle_input_element(array)[form.inc:893];
...form_builder(array)[form.inc:934];
....form_builder(array)[form.inc:934];
.....form_builder(array)[imagefield_zip.ahah.inc:88];
......imagefield_zip_add_files_to_form(array)[imagefield_zip.ahah.inc:16];
.......imagefield_zip_js(a:2:{i:0;s:13:"album_uploads";i:1;s:17:"field_album_files";})[?:?];
........call_user_func_array(a:2:{i:0;s:17:"imagefield_zip_js";i:1;a:2:{i:0;s:13:"album_uploads";i:1;s:17:"field_album_files";}})[menu.inc:350];
.........menu_execute_active_handler(a:0:{})[index.php:17];
..........index.php

Anybody have this issue?
(we've recently updated the module to support all files in the upload: http://drupal.org/node/1141534)