Redmine

Hello, I'm using Redmine 1.2.3. Wiki's topic that tells about bulk editing has this picture http://www.redmine.org/attachments/477/bulk-edit.png

Here we can see that Issues have different trackers and priorities and all items in context menu are active.

My problem is following. I want to delete subproject but want to keep issues so i try to move them to main project.
I can move each of issue separately. But when i try to move some of them at a time then "copy" and "move" items in context menu are inactive.
Can someone, please, tell me which conditions i have to satisfy?