Outlook 2003 needs username & password

Outlook 2003 is what I am running on a windows xp pro system. I access my .pst file on the server from my desktop pc. I never used to have to give any username or password just clicked and Outlook opened, Now I click to open Outlook and it takes about 3-4 minutes - then I get a box that asks for the user name and password to connect to the server. i just click cancel and then another box comes up and says operation failed . I click ok and then Outlook finally comes up. This whole process take almost 10 minutes. I want to know how to make this stop happening. Any idea out ther would be greatly appreciated. I run server 2003 on the server and all the permissions on the server are set so that I can access anything.