iMac Screen Horizontal Line Glitches
My iMac 21.5-inch, Mid 2011 has been experiencing a screen glitch for a while. Horizontal lines appear on the screen when scrolling, dragging windows, panning across the screen with my Magic Mouse. It looks like various parts of the screen are lagging behind others by fractions of a second. I can recreate the problem in any application.
Check out a video that I took of the problem here:
The graphics card is a AMD Radeon HD 6750M with 512 MB of VRAM. The processor is a 2.5GHz Intel Core i5. 4GB of RAM. Everything is factory installed by Apple.
Is this a software or a hardware issue? How do I fix this?
iMac, Mac OS X (10.7.2), 2.5 GHz i5; 4GB RAM; RadeonHD 6750M