Mac OS 10.6.8. In address book I have tried to delete some groups (created when I created an account in mail which I then subsequently deleted). However in address book edit the delete button is greyed out.

I cannot delete groups in address book because the delete button is greyed out. I have deleted the original mail accounts which created the address book. I could just leave the groups there but the problem it creates is that address book tries to connect to the relevant server every time I open mail, then I get various error messages because it cannot connect. Thanks for any assistance.