Managing scheduled posts have become a real pain recently.Since upgrading to WordPress 2.9.2 no matter what I try scheduled posts just do not publish.
So having trawled Wordpress.org I came across this plugin that will loop through your posts and force publish them if any are found that missed their scheduled publish time.
The plugin will check your posts every 10 minutes but the time interval is easy to change by modifying this line
Its not ideal but until this is fixed this plugin does the job.
You can get it from http://blog.avirtualhome.com/wordpress-plugins .