Another User is Currently Editing This Slice

This error message means that another user has the selected slice open and the structure cannot be modified while it is in use by the other user. 

This is typically a valid error message (meaning a users has the slice open), however this error can also happen if a user has a slice open and loses connection with the server or terminates their client without properly disconnecting from the database. 

This can be resolved by restarting the PowerOLAP Server Windows Service or Closing and Opening the Database on the PowerOLAP Server.

If you continue to have problems please let me know.