I have the exact same problem. No matter what I try, the problem persists, and I’ve tried basically everything that has been suggested in all the other “visual editor problem” threads.
Whenever I load the write page Firebug gives me this:
invalid property id
https://www.peterhengl.com/blog/wp-includes/js/tinymce/tiny_mce_config.php?ver=20080327
Line 37
When I click the “HTML” button I get this:
tinyMCE is not defined
https://www.peterhengl.com/blog/wp-admin/js/editor.js?ver=20080325
Line 73
I’ve really tried everything. Help!