Web service clients may encounter an error with the exception text "Internal SOAP Processing Failure" when consuming (calling) published BizTalk Web services.
Published Web services return the following generic exception when the Web service client encounters an error:
System.Web.Services.Protocols.SoapException:
System.Web.Services.Protocols.SoapException: Internal SOAP Processing Failure at
Microsoft.BizTalk.WebServices.ServerProxy.ServerProxy.Invoke....
Then Check the event log you will find these two errors :
The Messaging Engine failed to register the adapter for "SOAP" for the receive location "/VirtualDirectory/Name.asmx". Please verify that the receive location is valid, and that the isolated adapter runs under an account that has access to the BizTalk databases.
An attempt to connect to "BizTalkMgmtDb" SQL Server database on server "Server" failed with error: "Cannot open database requested in login 'BizTalkMgmtDb'. Login fails.".
To resolve this issue, configure the application pool identity for the Web service to use a user account that is a member of the BizTalk Isolated Host Users group. To do this on a Microsoft Windows Server 2003-based computer, follow these steps:
1.Start Internet Information Services (IIS) Manager.
2.Expand the computer name that you want to configure, and then expand Web Sites.
3.Right-click the virtual directory for the Web service, and then click Properties.
4.On the Home Directory tab, note the application pool for the virtual directory, and then click OK.
5.Expand Application Pools.
6.Right-click the application pool that you noted in step 4, and then click Properties.
7.On the Identity tab, configure the application pool to use a security account that is a member of the BizTalk Isolated Host Users group, and then click OK.Note This account must also be a member of the IIS_WPG group.
8.Exit Internet Information Services Manager.
9.Click Start, click Run, type cmd, and then click OK.
10.At the command prompt, type Iisreset /restart, and then press ENTER
May be there are other things casue this error , but this solution solved the error that I got...