It seems that there is a bug in the netscape 4.72 and also 4.73 version.
When one attempts to use netscape messenger and compose new message using
Address Book for filling 'To:' field, Netscape application crashes with
'bus error' message at moment when one have chosen the person on the list
and then clicked on 'To:' button.
*** This bug has been marked as a duplicate of 10433 ***