The comments are, notwithstanding the error message you see when you comment, being posted. We’re just not being notified when you do so we apologise if it takes a little longer to respond to your comments. I am curious is anyone else has experienced similar strange issues after upgrading to WordPress 2.1?
It turns out these errors were due to a classic case of RTFM (read the frikkin’ manual). One of the things you have to do when upgrading from a previous version of WordPress to WordPress 2.1 is actually delete all the WordPress files in your directory and upload a fresh set of files (just make sure you backup the directory first and restore all your customisations in the WP-Content folder as well as your wp-config.php file too – don’t delete these or you will have a completely empty blog). The instructions are here. Follow them to the letter!