Tried to look at your screenshot in another browser? Looks fine here (in Opera 24), which since it is a screenshot might be expected. That is, the problem is related to your hardware (as well as Opera), so looks fine on other hardware.
Best I can suggest is disabling hardware acceleration. Go to (Menu) > Settings and scroll to the bottom to enable the checkbox for Advanced Settings. A section named "System" will appear just above that with only one setting; clear the checkbox to disable hardware acceleration. As the description says, you'll then have to restart Opera to see if it makes a difference.