Hi,
I am also wondering about this..
1) It only happen with WP Edit, I had the old TinyMCE after I update it, I got a recommendation to update to WP Edit. I did as instructed, deactivate the TinyMCE plugin then deleted it. Then I installed the WP Edit from the WP plugins section. after the install I activated the plugin and was redirected to the 404 page.
Other plugins works fine.
2)If I try to get to the WP Edit settings page from the menu I get redirected to the 404 page
3)Yes, the plugin is activated.
Thank you again,
Dan