We are not able to reproduce your issue. The "put display to sleep" command, even using an hot corner to start it, seems to work correctly. We need more information on your specific setup. Could you please use the debug tool here
http://www.displaylink.com/support/ticket.php?id=269 collect the logs and post the zip file. It would help if you could switch the log verbosity to DEBUG (unplug and replug the adapter), try to put the display to sleep and collect the logs few seconds later. Thanks