"More than 1 heirachical taxonomy detected" error

Hi,
recently I’m experiencing a problem with this plugin. When I enable the post expiration on a post, whether there’s a default category set or not, and despite only one category is set in the post, and whether I set “replace”, “add” or “remove”, I always get the same message: ‘More than 1 heirachical taxonomy detected. You must assign a default taxonomy on the settings screen.’

Consequently the plugin doesn’t work. The problem affects the versions 2.1.1 and 2.1.0 as well. So I had to fallback to the 2.0.1 to have it working again.

PS: please note, also, in the error message, “hierarchical” has been typed wrong.

http://wordpress.org/extend/plugins/post-expirator/