Materialized view: compilation_error
It seems that Oracle doesn't like ANSI-style joins in the materialized view definition when refereshing...

Changing the definition to

create materialized view dept_emp_mv as  
   select dname, job, hiredate, count(*) as nbr  
               from emp e, dept d
               where e.deptno = d.deptno
               group by dname,hiredate,job;


makes it work for me.

See http://sqlfiddle.com/#!4/f706b/1

Changing the definition in the SQL Fiddle back to the one included in the question will cause the staleness to be COMPILATION_ERROR.

Personally, I would classify this as a work-around rather than an answer.