Some accounts that have observed this recently on edge:
Courses with CCX sections:Two are enrolled in CCX based off the root course https://edge.edx.org/courses/course-v1:MITx+8.APCCx+Summer_2015/info
1. Create course. In studio advanced settings, set "Enable CCX" to true.
2. In live course, instructor dashboard -> membership, promote a second account to CCX coach.
3. Log in as CCX coach. Go to instructor dashboard in the live course. Enroll third account as a ccx student.
4. Log in as 3rd account. Observe dashboard gives 500 error. https://edge.edx.org/dashboard