rectangular areas with colored squares on screen
Hello,
I have an iMac (27-inch, Mid 2010), with 12 GB 1333 MHz DDR3, ATI Radeon HD 5750 1024 MB
it runs macOS High Sierra, 10.13.6 (17G14042)
after running some time, rectangular areas with colored and textured squares appear, the react, flicker on and of, depending on mouse movements.
does anyone know what causes that and how to prevent that from happening
thanks!
Regards,
Wilfriedo
iMac