So I found the source of the problem. I have a small error in my POM file, and it caused the whole project not to build. Only after I built the project did I get past this error. Culd this be changed "NoClassDefFoundError" or something? That would make more sense?
Do you have Project -> Build Automatically enabled in Eclipse?
I agree that error message is not the best. If there's an underlying exception detail we should include the message in the dialog. It may be that the underlying top-level exception message is "WSDL generation failed" though. Rob would know for sure.