That's my code when I initializes swfupload in my javascript. I uses also the swfobject plugin. Don't care about "Explorer", it's an object that I creates for my program. I don't understand why my program works on IE7, firefox2 and 3, and not on IE6. It's very strange...

Explorer.swfu;
SWFUpload.onload = function ()
{
Explorer.settings =
{
flash_url : Explorer.basePath+"public/file/fla/gfx/swfupload_f9.swf",
upload_url: Explorer.basePath+"file/explorer/upload", // Relative to the SWF file
post_params: {},
file_size_limit : Explorer.maxsize+" KB",
file_types : Explorer.ext,
file_types_description : "All Files",
file_upload_limit : 100,
file_queue_limit : 0,
custom_settings :
{
progressTarget : "fsUploadProgress",
cancelButtonId : "btnCancel"
},
debug: true,

// The event handler functions are defined in handlers.js
swfupload_loaded_handler : swfUploadLoaded,
file_queued_handler : fileQueued,
file_queue_error_handler : fileQueueError,
file_dialog_complete_handler : fileDialogComplete,
upload_start_handler : uploadStart,
upload_progress_handler : uploadProgress,
upload_error_handler : uploadError,
upload_success_handler : uploadSuccess,
upload_complete_handler : uploadComplete,
queue_complete_handler : queueComplete, /// Queue plugin event
// SWFObject settings
minimum_flash_version : "9.0.28",
swfupload_pre_load_handler : swfUploadPreLoad,
swfupload_load_failed_handler : swfUploadLoadFailed
};

Explorer.swfu = new SWFUpload(Explorer.settings);
}

After that, I tries to replace all my settings of event handlers by : "this.swfUploadLoaded this.fileQueued, ... . I've got an exception in SWFUpload.prototype.initSWFUpload when loadFlash() is called... !!!

Do you have a handlers.js file or have your functions all defined. Since you are using SWFObject you should make sure that your functions are declared early or included near the top so you can be IE realizes they are there before it tries to kick off SWFUpload.

Somewhere you need to declare your event handlers:

function swfUploadLoaded() {

}

function fileQueued() {

}

P.S. If you aren't specifically using those events for anything then do not include them in your settings.