Some server configurations running Pure-FTPd have trouble updating WordPress via FTP. Common error messages when trying to update WordPress or update/install a plugin look like this:
- Could not copy file.: /wp-admin/css/theme-editor.dev.css
- Could not copy file.: /public_html/wp-admin/css/theme-editor.dev.css
- Could not copy file.: /.../.../wp-admin/css/theme-editor.dev.css
- Could not create file.: /public_html/
Each of these cases seem to be related. There is a patch going into WordPress 3.2 that should take care of the issues and the plugin will be obsolete after updating to that version (
http://core.trac.wordpress.org/ticket/10913). In the meantime, install and activate this plugin. Updates should work as expected.
Upload the FTP Upgrade Fix plugin to your blog via FTP and Activate it.