I thought that you had to use a special domain group with xp networks? Otherwise you'd get strange errors like that one - as it automatically assigns privledges based on the domain group policy?
Have a look here (quick google found it .. it may not be 100% suitable for you :o))
This email and any attached files are confidential and may
be legally privileged. It is intended solely for the addressee.
Access to this email by anyone else is unauthorised.
If you are not the addressee, any disclosure, reproduction,
copying, distribution, or other dissemination or use of this
communication is strictly prohibited. If you have received
this transmission in error please notify the sender immediately
by telephone at ++353 1 6035800 or email emailadmin iibbank ie
and then delete this email.
Email transmission cannot be guaranteed to be secure or error free
as information could be intercepted, corrupted, lost, destroyed,
arrive late or incomplete, or contain viruses.The sender therefore
does not accept liability for any errors or omissions in the contents
of this message, and shall have no liability for any loss or damage
suffered by the user, which arise as a result of email transmission.
If verification is required please request a hard copy version.