Every time I press the queue tab in the render window, the program freezes. I have tried multiple files with the same result. Before yesterday I had never had this problem. I am using a 64 bit PC on Windows 7 with Keyshot 6 Pro installed.
Are you out of disk space by any chance?
This could also be caused by a corrupted queue file.
Please go into your _Documents/KeyShot 6/Scenes_ folder and delete the q.xml file. This will clear your queue and any jobs will need to be re-submitted. Restart _KeyShot_ and attempt to queue render once more. Let me know how this works out for you.