Published form won't connect to data source

[Kolten]

My form uses a datasource that is a web service that outputs XML so that I
can dynamically load a listbox. Simple.
The form works wonderfully from my local machine.
When I publish the form to SharePoint 2007 as a content type though, I get
an error stating it can't access the data source.
I am unsure how to proceed further without more information. Am I looking
at an authentication issue? Which authentication issue? Where? What user
does infopath forms published to a sharepoint server use to authenticate
with? My user account? If so, then why does it work from my local computer
when selecting "Preview form"?

A little about the web service:
It's output looks like:
<users>
<user>
<value>[email protected]</value>
<value>[email protected]</value>
<value>[email protected]</value>
</user>
</users>
It uses an LDAP connection to access our Active Directory server and pull
email addresses (amongst other information) from it. It authenticates via a
service account I created called "LDAP".
I don't think this authentication should matter though, as the service works
on it's own, and when called from Infopath designer.
It's only when the form is published do I get an error.
Any ideas/thoughts/suggestions? Even suggestions I could use to debug this
one? The error message I am getting isn't very profound at ALL.
Thanks.

 

[S.Y.M. Wong-A-Ton]

Have you already seen this article?
http://msdn2.microsoft.com/en-us/library/bb787184.aspx