If the GUI runing computers are out dated and using first generation of video card then GUI fails to get the hardware video acceleration which is required by the graphical components of the GUI and as a result GUI runs slow and crashes on start up or does not respond at all.
You can disable the high contrast style from the advanced settings of the GUI. If the numbers of users are quite high under department or custom created groups then you can try to put the users 10 or less than 10 under departments.
Finally if the GUI still crashes on start up then you can disable the use of hardware acceleration of the video card by adding blank text file named nohwfx in the Advanced configuration folder of the GUI.
