The error you are seeing is with regards to disable operator feature I guess.
Login with any known operator, go to list of operators (records->organization->operators) and open the operator. In the security tab you will see disable operator check box. Uncheck that, set a password and you are ready to go.
In Pega 8.1, when you import any application by default the operators will be disabled and you need to choose enable existing operators option while importing the RAP file so that the import operation wont disable the operators. If you miss this step then you should open the operator records which belongs to your imported RAP and enable them.