Well I checked the instructions twice and I couldn't find any error. The others didn't say it doesn't work so I don't know what has gone wrong with your installations.
Do you have a backup of editpost.php and functions_newpost.php? Take the old files and modify them again to make sure you have the right code. You could even send those files to me and I'll take a look at it. Use dienase [at] gmail.com please