Does it still happen on the motherboard's onboard graphics? I only seem to get the same problem when I set my taskbar to autohide, so its hard for me to figure this out
By the way, when did this start happening? When you got your monitor? Graphics card? New motherboard? If you tell me what you did with your PC around the time it happened it can assist me in troubleshooting.
And see if you have the latest AMD Drivers. It is listed on AMD's website that AMD Catalyst Control Center is the driver for it; said here: Catalyst™ Drivers for Radeon™ R9 200, R7 200, HD 7000, HD 6000 and HD 5000 Series.
These drivers are listed for Windows 8.1 and 7. Try those. And here is the site for you:
http://support.amd.com/en-us/download