sharepoint gets authentication logon when opening up office

[mrdamo]

sharepoint gets authentication logon when opening up office documents externally. Has no authentication prompts when opening internally on the same domain.

Is going through Citrix Netscaler not an ISA server.

Use SharePoint WSS 3 SP2.

authentication type is windows NTLM with client intergration enabled.

any ideas without changing clients IE settings if possible?

Vendors and external users will be accessing this from different non work pcs.