Diagnosis
A single selection that no longer exists is being refered to.

System Response
The system will delete the reference to the single selection that nolonger exists. A reference to a new (empty) single selection will becreated to restore the formal consistency in the customizing settings.

Procedure
If you save the settings, the system will store the reference to the newsingle selection in the database. Check the new single selection createdby the system and adjust it if necessary.