This error can occur when multiple computers within the same network have the PayClock software installed running their own database. When multiple PayClock databases are running within the same network they will interfere with the connection to the local database because they broadcast on the same TCP port 2638 so the first database up and running on the network will prevent the other database service from starting resulting in it attempting to connect to the other computers database. If the software is not licensed for the multi-user the single user error will occur.
To resolve this issue you will need to uninstall the PayClock software from the computer that does not need to have it and then reboot the computer that should be running the database. Once the computer has rebooted the database service will start up and you will once again be able to access the PayClock software.