Open a Word doc in Outlook 2007 prompts for internet id & password

[PattiK]

As the subject indicates, when I open an email message that contains a Word
document, I am prompted for my internet credentials. I am running Outlook
2007 and am attached to a LAN. This only happens with Words docs, not other
attachment types. If I enter my credentials and later go back and open the
same file, I am not prompted again, only the first time. I am also not
prompted if I save the attachment to my hard drive and open it from there.
That says to me it's not a Word issue, but some setting in Outlook? Any ideas?

Thanks.....Patti