I've noticed using Netscape 4.61 that while entering data in the "New card" dialog box, the user cannot use scroll bars in the Netscape mail (messenger) or browser (navigator) windows. Unless there's some reason this functionality is supposed to be disabled, this may be unnecessary. In fact, if you want to add a "New card" and you need to scroll up through past mail to make sure you get the e-mail address right, you can't do what you need. It's simple to reproduce: run messenger on netscape 4.61, bring up the address book (Communicator -> Address Book) and then try to access one of the scrollbars in the messenger widget. On my machine, I can't get it to work.
Yup, it's a bug. Reported to Netscape.