When trying to create a new schedule in MMEA 7.6 the following error is returned: "Server Error in /MigrationManager Application - Index and length must refer to a location within the string. Parameter name: length"
After this error is returned then 'System Configuration' is no longer accessible.
This issue has been resolved in Migration Manager for Email Archives version 7.8 which is due for release in the Fall of 2017.
If this issue is being experienced and a fix is required prior to the 7.8 public release then please open a service request with Quest Support.