Integration

There are a lot of people having the same problem here. I'm making a very simple BPEL process that calls to a Web Service developed in ASP .NET running in IIS. But I can't deploy the process successfully because i'm having errors about different types of variables in the assign activities. When I try to explore the variables I have always the same error: Exception: Problem building schema! I haven't imported any schema because I don't have any .xsd file so I don't know what's my problem. Can anybody help me?? Thank you :)