Well, with desktop graphical interface and video glitches and freezes, one of the first things I usually consider is whether I'm using the right video driver or whether the video card is going bad. Some video cards (such as Nvidia) often work better when installing and using the proprietary (but freely available to Linux users) Nvidia driver. In Linux, this can usually be installed using the "Hardware Drivers" or "Additional Drivers" or "Driver Manager" section of the system preferences.
Linux will often install the open-source "nouveau" video driver for Nvidia cards, but Nvidia's own driver for that model will often work better.