When I edit a policy that has multiple choice list boxes (e.g. content/edit) and I remove nodes or subtrees from that policy the items I've selected in the list boxes are reset.

Steps to reproduce

• create a new role with a policy that has limited access to content/edit
• edit that policy
• add a node or subtree to that policy
• in the class selection box select some class
• check the checkbox in front of the added node and click "Remove selected"

After deleting this node, in the class selection box the class we have previously selected is not selected anymore.