This happens in Chrome and Firefox.
When CTRL + click is pressed on a case in waiting, and reassign is clicked in the workflow of the new tab, the drop down menu for users is not showing all users.
In 7.2a1 you can click the Magnifying glass to change the user to System administrator and then the dropdown menu should show all users.
This is currently with development and should be fixed in a future version of sage CRM.
New tabs do not work on anything after 7.2a1 as frames have been removed.