Do the errors go away if you remove the DOM?
Hmm, no, the errors are still there, even though DOM is removed... So I guess DOM is not the issue...
Ok, I think I've solved the problem. I simply commented out line 86 and 187 in modeladmin.js
//tinyMCE.execCommand('mceRemoveControl', false, $(this).attr('id'));
I know it's bad practice, but since I don't use tinyMCE anywhere, it really doesn't matter.
Thanks Uncle Cheese for your support anyway...
There's a patch for that floating around somewhere. Just look up "tinymce modeladmin" in the forum.