cannot be cast to com.webmethods.caf.task.core.model.ITaskClient during creation User Task in BPMS

I’m trying to create user task implementation in BPMSProcess, and afer: right click on User Task->Create Implementatio->New User Task… and choosing e.g default wizard i’ve got: cannot be cast to com.webMethods.caf.task.core.model.

Does anybody know how to solve this?

I am also facing the same issue,please help me on this.