WORKAROUND:
Instead of having to close Toad to terminate the threads, the threads can be cancelled through the Object Explorer.
1) In the Object Explorer, display the list of Subsytems and highlight the subsystem the thread to be terminated is for.
2) On the right hand side of the Object Explorer, click on the Threads tab. If the right hand side of the Object Explorer is not in view, right click on the highlighted subsystem and select View Details.
3) In the Threads tab, right click on the thread to be terminated and select Cancel Thread.
STATUS:
Waiting for fix to be released in a future version of Toad for DB2.
