When we upgraded to WordPress 3.1 we noticed that one of our open source plugins, Simple Crumbs which produces breadcrumbs like this:
suddenly stopped working! WordPress indicated that “Simple Crumbs has been disabled” as it has an invalid header. Well the good news is the fix was quite easy. We hope the official plugin will be updated soon. In the meantime we have attached simple-crumbs fixed for use in WordPress 3.1.
As the plugin is GPL v2 open source, we are permitted to redistribute it here free of charge.