K2 Server/Service error "String cannot have zero length"

Posting this topic for general reference:

This error message can be displayed in both Console mode or Server modes.

Typically this error is generated due to records/values in the K2 database's _Setting table were missing, but are required for the K2 Service to know which user manager to load.

1. In Services, stop the "K2.net 2003 Service"
2. In the K2 database's "_Setting" table, restore these missing settings
2.1 UMAssembly ="ADUM" (no quotes)
2.2 UMType = "ADUM.K2UserManager" (no quotes)
3. In Windows Services, restart the "K2.net 2003 Service" or start K2 Server in Console mode if preferred

If step 3 fails to resolve the issue, reboot the machine (the K2 Service may be in an unstable or locked state).

The cause of the missing settings is difficult to determine. Typically, it is suspected that a user has manually altered the table records/values since the settings are only captured/updated during the original K2 installation and/or when SQLUM is installed.

The errors may not be realized until the K2 service is stopped and restarted (the settings are read only once during startup).

See the attached document for screen shot examples.