I got the same problem - haven't got any answers though.
Is remote desktop correctly configured in My Computer > Properties?
Is your installation a clean install of XP Pro or and upgrade?
Is your PC part of a domain or stand alone?
My pc is in domain and has a clean install of XP. The remote desktop
connection has been working just fine a long time, and it is now
lately that it has stopped working. I have also reinstalled XP without
any luck for the remote desktop