Plugin: TinyMCE installation error

When trying to install the TinyMCE plugin, I get an error message. I think it started because I accidentally installed the TinyMCE Advanced first. I deleted it from the /wp-admin/plugins.php page, and then I removed both plugin folders (tinymce and the advanced folder) from the wp-content/plugins folder on my server.

But when I try to re-install the TinyMCE plugin (by adding the installation zip-file via the /wp-admin/plugin-install.php page), I get the following error message at the top of the screen:

Warning: include_once(/customers/lc-norway.com/lc-norway.com/httpd.www/wp-content/plugins/tinymce/) [function.include-once]: failed to open stream: Success in /customers/lc-norway.com/lc-norway.com/httpd.www/wp-settings.php on line 465

Warning: include_once() [function.include]: Failed opening ‘/customers/lc-norway.com/lc-norway.com/httpd.www/wp-content/plugins/tinymce/’ for inclusion (include_path=’.:/usr/share/php’) in /customers/lc-norway.com/lc-norway.com/httpd.www/wp-settings.php on line 465

I guess this means that the plugins have changed something in the wp-settings.php file, but I tried uploading a clean version from my harddisk, and I still get the same error message.

Deleting the tinymce folder from the wp-content/plugins folder removes the error message from the site.

So, what’s wrong? What do I do to set everything back to scratch and start an entirely clean installation of TinyMCE?