can approve but can't delete

in the permission setting all boxes were checked for registered user, and none checked for anonymous visitor. The comments are displayed on the author's node with both an 'approve' and a 'delete' link. 'Approve' works, however, when 'delete' is clicked, the user is led to http://domain.com/usercomment/delete/13 with the following error

Access denied
You are not authorized to access this page.

Can someone shed light on this?

This is a very useful module for a community site. Surprised the feature wasn't in drupal comment module. Kudo for the work and thanks much!

- Alan