Specific users slow to access file shares to a server across the WAN

Hello all,

We have two users that currently experiencing painfully slow performance accessing files on a file share in a server present across the WAN. We have tested accessing the same folders and files with other accounts that have the exact same access rights and everything works fine. Access times experienced by virtually all other users is fast and without issue.

We have done the following:

1) Logged in with other accounts in the trouble user's XP machines. Performane was normal, so this lead us to believe that the issue was not on the users' computers.

2) Logged into our own XP machines with the trouble user's accounts. This produced slow performance. This lead us to believe that the issue was the users' accounts.

3) We analyzed the users' AD group memberships and cross-referenced these. We found several matches and removed those group memberships for test purposes. This did NOT fix the issue.

4) We created a new account as a copy of one of the trouble user's account. This coped all of the original user group memberships into a new account that had a new SID. This ALSO produced slow performance.

5) We created a test user from scratch that had no other membership other than Domain Users. This ALSO produced slow performance.

6) Lastly, we tested again with our OWN accounts and this produced fast performance... We re-confirmed that nobody else, other than the two users referenced, were having any issues.

I am now 10 hairs balder and still do not have a solution. Your help is deeply appreciated.
Thanks.