/node/add/simplenews showing non-clickable fieldsets and FCKeditor not showing up in the body textarea

Drupal 5.18, this happens with Firefox 3.0.10 but not with IE 6.0

Using a small hacked bluemarine theme, tried with garland and problem remains.

Only in /node/add/simplenews fckeditor rich text editor does not come up and after the send block fieldset all other fieldsets (workflow, ...) are collapsed and non-linkable. Titel, taxonomy and body fields are ok, except that the body does not show with the fckeditor. For all other node types fieldsets are OK (clickable if collapsed) and FCKeditor shows up when it is supposed to show up, so this seems something specific of simplenews or an interaction with other modules. The only related issue that I found is quite all and not specific to simplenews, but seems similar: http://drupal.org/node/104175 . Here it says that there may be an interaction with the upload and nice menus module. I don't have nice menus installed and I tried disabling the upload module but the problem persists.

In Internet Explorar 6 everything comes up without problems.

Even without the fckeditor module not installed, the fieldsets appear as collapsed and non clickable.

Versions installed
fckeditor module 5.x.2.2 with FCKeditor 2.6.4
simplenews 5.x-1.x-dev

The body form appear as a double textarea (first screenshot). The non-clickable fieldsets are shown in the second attachment after the send block.