We have one site attachment Document Library in MOSS 2007 (SP2) which contains word documents.
when we are trying to view the attachment even if user has requrired permission for this list, System open a log in page in
a pop up. The user can either log in again and then close the popup window or he can simply close the log in window, and
then the document opens up. This problem occurs only in some of the machine only even with same IE version.