If an error appears in the Output Window or an operation fails to complete, you can see the status of the CMS commands involved by clicking the Explorer Runtime tab.
The Undo Check Out command failed because the file was not reserved
You can right-click a command and select View Output to see what part of the error output is accounted for by the particular command.
If a command appears with a green arrow, it means that the command is unable to complete execution. If that is the case, the CMS Support Module will not function correctly until the hung command is killed.
To kill a command