Wireless access

I have a few users using Wireless access to my network. Everything is cool. One user downloaded Service Pack 1 for XP and loaded it on his windows XP Home laptop. Now all of a sudden he can’t acess the one Windows 2000 server. I can access all the other servers by putting in his user name and password for the network but the 2000 server says he doesn’t have permission anymore. What changed?? Help!!! That’s where all the database he works with is stored. Hard wired it’s fine with the user name and password, just bad wireless. Help!