problem seems to be a javascript error

Perhaps, no JS Files are included in template, did you use garland theme for testing? Please show me a example of generated source code when visting node/add/image .
What browser do you use? Have you read the project page?
In the moment, it’s sporadically not working with IE 7, but this is a bug of swfUpload (Google Code #2044). There are also sporadic problems with other browsers, except Firefox. Perhaps you could help me =)

If the select button does nothing, then this should be a bug of swfUpload, not of this module.

Please show me the generated source code when visiting node/add/image (important). There should be some entries which include the JS Files (should be generated automatically):

...
<script type="text/javascript" src="/drupal6/sites/default/modules/image_fupload/swfupload/swfupload.js?m"></script>
<script type="text/javascript" src="/drupal6/sites/default/modules/image_fupload/swfupload/swfupload.queue.js?m"></script>
<script type="text/javascript" src="/drupal6/sites/default/modules/image_fupload/swfupload/fileprogress.js?m"></script>
<script type="text/javascript" src="/drupal6/sites/default/modules/image_fupload/swfupload/handlers.js?m">
...

(for example)

But it could be that your theme does not allow adding any JavaScript-files. Is a $header variable set in theme? For testing, you could use "garland" theme. Please inform me whether it works with "garland" theme or not?

Did you install Flash 9.* correctly on your computer?

Another test

Try to upload some data at http://demo.swfupload.org/simpledemo/index.php . Does it work there?

Flash object is embed later by JavaScript, so you can't see one in source code. But it sounds very strange to me that the multiple Upload Demo works but the SimpleOne not. I will look for differences between them to provide a better javaScript handling. This will be done in the next few days. Thanks for these information.

This version is bad because it should be "9.0.124.0 Linux" or "9.*", "10.*" is not supported yet by swfUpload. Nevertheless I will analyse this case and try to understand why especially "Multiple Instance demo" works, but "Simple Upload Demo" doesn't work.
This could take a few days, of course, patches are welcome.

Now, myself I tested this case on Ubuntu 8.04, Firefox 3.0.1 & Flash Linux 9.0.124. I tested all demos on swfUpload, but none of them really works. Also the multiupload demo doesn't work, it only pretends that images are uploaded, but nothing will be sent to server. This sounds like a Flash Player or swfUpload bug, I will ask the maintainer of swfUpload for help =)

same problem here with 6.x-2.0-rc1.
nothing happens clicking on the upload button.

firebug:

syntax error
[Break on this error] var settings = {\n

the html looks this:

window.onload = function() {
var settings = {
flash_url : "/drupal/sites/all/modules/image_fupload/swfupload/swfupload.swf",

guess there's a problem with this linebreak...

I don't get this error, please let me know more about your system's configuration, Flash version and so on, otherwise it's difficult to find that problem.

Try to update to Flash 10 and Image FUpload 2.0.
Because of no activity for so long, I will mark this problem as fixed.

I am having the same issue as above.

I just updated the module to 6.x-2.0-rc3. This had worked a week or two ago when I last used the older version, but now it doesn't work. All required files are in the proper directories (root/modules/image_fupload/swfupload), and are being called properly in the header. I just get a non-functioning "select images" button. When I click it, an error gets thrown. Tried it using FF2 and IE7 and neither work.

Firebug's error is "swfu has no properties onclick(click clientX=0, clientY=0)" in image (line 1)

[edit]

Sorry - I don't know why it says status is fixed. Won't let me change it on edit.

[edit 2 - more info]

There's another error I did not notice, on page load before I click the select images button (from firebug):

"uncaught exception: Could not find the placeholder element: spanUploadButton

Line 0" and there does not seem to be any element name with that ID.

I also see that the js is calling an image which doesn't exist: select_images.png

I'm getting the same as #13, also this message in firebug when I try to click select image:

swfu is undefined
onclick()image (line 1)
[Break on this error]
image (line 1)

I'm getting this error in chrome (is doesn't work in ff, ie either):

Uncaught Could not find the placeholder element: spanUploadButton http://www.eendje.be/modules/image_fupload/swfupload/swfupload.js?q (line 44)

Extra info:
* Versions: SWFUpload v2.2.0 Beta 4 Core, image_fupload-6.x-2.0-rc3, drupal 6.8, flash 10
* The simple demo on http://demo.swfupload.org/ works for me
* Js on the page:

    <script type="text/javascript" src="/modules/jquery_update/replace/jquery.min.js?q"></script> 
<script type="text/javascript" src="/misc/drupal.js?q"></script> 
<script type="text/javascript" src="/files/languages/nl_6ea0783e90bfbae60832928962e3a056.js?q"></script> 
<script type="text/javascript" src="/modules/acidfree/acidfree.js?q"></script> 
<script type="text/javascript" src="/modules/image_fupload/swfupload/swfupload.js?q"></script> 
<script type="text/javascript" src="/modules/image_fupload/swfupload/swfupload.queue.js?q"></script> 
<script type="text/javascript" src="/modules/image_fupload/swfupload/fileprogress.js?q"></script> 
<script type="text/javascript" src="/modules/image_fupload/swfupload/handlers.js?q"></script> 
<script type="text/javascript" src="/modules/pathauto/pathauto.js?q"></script> 
<script type="text/javascript" src="/misc/jquery.form.js?q"></script> 
<script type="text/javascript" src="/misc/ahah.js?q"></script> 
<script type="text/javascript" src="/misc/progress.js?q"></script> 
<script type="text/javascript" src="/misc/autocomplete.js?q"></script> 
<script type="text/javascript" src="/misc/collapse.js?q"></script> 
<script type="text/javascript" src="/misc/teaser.js?q"></script> 
<script type="text/javascript" src="/misc/textarea.js?q"></script> 
<script type="text/javascript" src="/themes/acquia_marina/script.js?q"></script> 
<script type="text/javascript"> 

Edit 1:
After clicking on the "select images" button, i get this:

Uncaught TypeError: Cannot call method 'selectFiles' of undefined http://www.eendje.be/node/add/image (line 318)

I don't know why, but something went wrong in CVS, so a complete rewrite (version 2.1) which is based on devel version, will be published.
Try out version 2.1.

Sorry for the trouble.