WIN 2003 SERVER DOMAIN USERS

We have a server running on win2003 server and 6user machines all on win xp sp1.we all log in to a domain on the server with assigned usernames and passwords–me and our accountant log in using the same username and passwords and all has been well till last week when both our comps take tooo looong to log in and at times even hang but when loging in to the local machine (not domain) its very fast. The computer account we log in with exists. Ow can i solve this or better still ow can i create a new user account to log in to our domain coz when i try i get the msg the computer was not found. pls hlp