Remote access error 721

I have a client that is trying to use RRAS to connect to the server. They
have about 15 remote users and all but one are getting in ok. He gets an
error 721 when trying to connect. I have made sure that all the firewalls
are off (except Windows Firewall which is controlled by Group Policies). I
have tested diffrent computers from his home office and all of them can get
in. I have also tested his computer in diffrent remote locations that are
known to work. I have tested his account on other computers and all work
fine connecting. That only leaves the computer itself. It is an XP Pro with
SP3 installed. I have ran virus scans and udated the network drivers. Any
ideas would be creatly appreciated.

Thanks in advance,
Chad