Debug SWFUpload error in Chrome

The script to debug is at <[login to view URL]>. The SWFUpload widget only allows a single file selection, and the upload starts automatically once the file is selected. It works fine under other browsers, but Firebug in Chrome shows an uncaught "Call to ReturnUploadStart" at line 452 of swfupload.js. When someone using Chrome clicks the "Upload" button and browses to a zip file, the progress indicator hangs at "Uploading..." I need to know what I need to do to get this thing working under Chrome.