Stop all Authenticore servers.
Use one of the servers to generate a new Enterprise Key. After the Key has been generated, start the server.
Start other Authenticore servers. Obtain the Enterprise Key on each of them.
After a new Enterprise Key has been generated, all data encrypted with the previous Key become unavailable, and you will receive the error message every time you open the NetIQ tabs in ADUC snap-in.
If new enterprise key is generated to replace an old one, then password reset is required for activating user accounts that worked with the previous enterprise key.