"Make sure the commentform options are set" -> means?
I use FF 7.0
...ahhhh I think I found it. I had colorbox plugin disabled and then the addcomment button has no function when clicking it (only) on the stopdesign image.php page. (album view is ok)
Now I enabled the colorbox plugin and voila... also the addcomment button on the image view page works now when I click it.
How can that be that this colorbox plugin has an effect on that addcomment button!? strange thing imho