After upgrading to WordPress 2.9, self-hosted WordPress installations may receive this error:

Call to undefined function ctype_digit() in /wordpress/wp-admin/includes/file.php on line 238

When trying to use either the Flash uploader or the browser uploader to upload new media to WordPress, or when trying to save a new post as a draft, post it and so on. This happens because PHP on your host has not been compiled with ctype support. Simple to fix, if you have control of the host, make sure that you pass the --enable-ctype flag to the configure program when you compile PHP. For more information check here http://us2.php.net/manual/en/ctype.installation.php.

If you happen to be using FreeBSD and PHP5, simply install the textproc/php5-ctype port, and reload your Apache.

Trust this helps out some folks.