InfoPath Dev

I have an InfoPath 2003 form which lives in a SharePoitn form Library.  This form writes to a SharePoint List via web services.  The form can write just fine to some dummy lists I have within the same site as the form library.  However, when I attempt to write to the actual SharePoint List in a different site and different site collection, I get a System.Net.WebPermission error.  I do have contribute access to the list, and can write directly to it, i.e. outside of InfoPath.  The form is domain security level and the zone is Intranet (I have read Halstead's et al. book -chapter 8).  I shouldn't have to make the form full trust (besides that would take a miracle to get by our security folks this century) as it works within the same site collection - which tells me the managed vs unmanaged thing is not an issue. 

The site collections are in different managed paths if that makes a difference. 

Learned some more on this....

Apparently managed paths are in different web apps, at least they are here.  The problem seems to be an InfoPath form writing to a list outside of its own web app with Domain Security Level.  What makes this confusing is that our web apps are within the same Domain.  I am now wondering if I am misunderstanding the definition of Domain within the InfoPath world.   

 I do know that if am going through debug mode/preview I get the same error as above when writing to a list.  I have to publish and test from where I published.  Again, my local machine and the site I am writing to are in the same logon Domain. 

 So, now my question is does Domain Trust mean trust within the same logon domain, web app, or something else?