WYSIWYG tinymce asset plugin problem

I use the WYSIWYG-tinymce as editor and i want to import images,files,... from my asset module to my editor. I used the information on this page (http://drupal.org/node/209509) to plug assets into tinymce. I use tinymce version 2.1.3. This works fine in Internet Explorer 7, but in firefox 3.0.6 it gives all kind of trouble, I think it has to do with the order in which the javascript files are read. Does anyone has a solution or patch for this.

A side remark:
Is tinymce 3 compatible with drupal 5? And could the asset plugin als work under tinymce 3?(I tried it with no result)