User can't connect to particular webserver from his PC.

Hi,
I am running into a strange problem. Let me begin with a few facts:
-We are on Active Directory
-Webservers are win2k3
-Client is on XP professional
I have a user that is not able to access a website running on a
particular server. All other clients are working fine, however this one
user is not able to access any website running on ServerX. He keeps
getting prompted for userid/pass, and when he enters it it let's him do
it three times before throwing an unauthorized to view this page error
page.
Some more facts:
-It's not an issue with the user, as he can access this website from
another PC.
-He can access other webservers in the domain from his PC fine (in fact
there is a development server (ServerA) that is set up exactly the same
as ServerX). He can access ServerA with no prompts and no issues from
his PC, but not ServerX.
-There is no special security set on ServerX (i.e. restricted ips,
etc...)
-His IE settings on his PC are all fine, and match other users (who
don't have any issues), authentication settings, advanced settings,
security, etc...
-He can access the website on ServerX from his PC using the sites IP
address in the URL, but that messes up kerberos authentication which is
required to get to the backend data.
Is there anything else I can check on his PC that would not allow him
to access serverX.

Any help would be greatly appreciated.
Thanks,
Tom

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