I was having numerous issues getting my orchestration to work, that I had published as a web service. The problem was calling it from my .net assembly.

My problem was the debug processes stopped here: Internal SOAP Processing Failure

Stack dump: at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
   at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)

We discovered that we needed to add the user who runs the app pool for the web service to the IIS_WPG group and to the "BizTalk Isolated Host Users" group. (Plus ASPNET on win xp)

This worked fine on the dev box as all groups are local groups. But on a rig you need to take into consideration, that the "BizTalk Isolated Host Users" group is a domain group, and the IIS_WPG group is a local group.

So you need to remember to work at the domain level as well as the local group level, something you need to take into consideration for production rigs. Not everything that works on the dev box, works right away in production.