Jason, thanks for your reply.
On my page the update/insert form is generated by Dreamweaver Developer Toolbox and has an insert/update server behaviour.
When I don't use the HTML editor on this page, inserting, updating and saving text in the text areas works just fine. All my edited text is stored without any problem in my MySQL table. And retrieved correctly.
When I then add HTML editor to my page and retrieve text for the first time, the previously stored text (so without the editor) is still retrieved correctly. But as soon as I click the "Update" or "Save" button, the text is lost (and not stored again). The text field remains empty when I try to retrieve the text once again from my database table.
Newly entered text disappears in the same way.
Any clues? Thanks in advance.