In an Enterprise Service Tools single-service project, if you are running (1) Create New Service Implementation (top-down) scenario or (2) Map to an Existing Service Interface (meet-in-middle) scenario, with the WSDL file (that was originally imported from a remote location) that contains, includes, imports, or redefines a schema, fail with an error.
RMB -> Import -> Source files and try the top-down scenario.