Outlook 2000 problem

When a user opens her outlook, this message appears “The name could not be matched to a name in the address list”. Once she clicks OK, an Exchange settings window will appear with the server name filled in correctly and the user name field filled with *Unknown*. If I erase that, type in the user’s name, and click check name, it will underline it. I will click OK and it lets me in to her mailbox. She has to do this every time she clicks on the Outlook icon. I’ve checked the Mail settings within Control Panel, make some changes to see if it works but it never stays. I tried logging in to that workstation to check my email and it works for me and at least 1 other person. Any ideas on what else I can do to fix this? Unfortunately, the exchange server is managed at another location and I don’t have access to it.