In Console you will see an 'Object Reference' Error when you go to the File menu and select "Unlock Item"
The intended use of locks is to stop others from changing the contents of records when another user is in them.
However you can at some points have an unintended locks in your lock table, which is what is causing this error message. This can occur if the Incident window hasn't been closed properly by the User, for example if you close your browser without first clicking cancel on the Incident.
The problem with unintended lockings is that the Background Services can't automatically unlock these like it does with all intended lockings every 20 minutes so these Incidents will stay locked.
The way to temporarilly fix this is to clear out the 'tps_lock_item' table by running this script:
delete from tps_lock_item
We have also written a trigger for you to add on your database which will remove any unintended lockings as they occur in the databse and therefore fix this problem for you. You will find the trigger attached - use the .sql version for MS SQL Server or the .ora version for Oracle.
This has been registered as Problem: 4436 and occurs from version 7.3 onwards. If you are experiencing this, please log an Incident with your Support Provider and refer to this reference number.