Hi,
I'm also seeing and replicating this issue. I just purchased three monitors. I have a Radeon 7850 driving two monitors via HDMI/DVI and the third monitor using the onboard Intel graphics (core i5 ivy); even tried running two monitors for the onboard and one on the discrete. This is on a Z77 chipset (Gigabyte UD5H). Happens all the time when moving the mouse over an area that causes the mouse cursor to change.