Deploying EDMS Custom Webservice to IIS

Hi,

I've developed some code in visual studio 2005 to provide a webservice for making alterations to AD via EDMS. The webservice uses a library that I have made for doing these alterations. This library can run in either LDAP or EDMS mode, running in LDAP works fine when deployed to IIS (on 2k3 x64 Server) but when using EDMS, I get

System.Runtime.InteropServices.COMException: Unknown error (0x80005000)
   at System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail)
   at System.DirectoryServices.DirectoryEntry.Bind()
   at System.DirectoryServices.DirectoryEntry.get_AdsObject()
   at System.DirectoryServices.DirectorySearcher.FindAll(Boolean findMoreThanOne)
   at ADInteractor.FindUsersByPartalLoginName(String name) in C:\proj\ADInteractor.cs:line 278
  
HOWEVER, using the visual studio in-built webserver, both EDMS & LDAP work fine. Both machines have the ActiveRoles Server 5.2.4 ADSI Provider installed on them. The only difference being that I'm developing it on XP x86, and the IIS server is 2K3 x64.

The app-pool that the web service is running under is running under a domain username, and the web.config file has the identity impersonation set to true and also set to this username. I've tried various combinations of setting it on and off and have added the domain user to the local admins & IIS WPG group on the IIS machine, but none of this has helped.

Any ideas?