In the configuration program (configtool.exe in the install folder) check off the 'Use AlphaBit' option. That should avoid problems with graphics cards that do not support colour keying, which will cause a similar problem (black boxes around items/characters).

Also in the configuration program, try switching to Software rendering, rather than Direct3D, or lower the game resolution, to see if that will make a difference.

Try rebooting your computer, if you haven't done so while troubleshooting. If I leave mine on long enough, eventually I'll get a different graphical problem (dark shadows and rainbow colours underground or at night), until I reboot (though it can also sometimes go away on its own, as well).

Try the Windows 8 Performance "Patch" (works in Win 7 and 10, as well). That can help with some graphics issues.

In the Divine Divinity install folder, try right clicking on the div.exe program file, select Properties, switch to the Compatibility tab and try different compatibility modes. In Win 7, disable desktop composition and check 'Disable display scaling on high DPI settings'; for Win 10, check 'Override high DPI scaling behavior' and set it to Application.

You can try using the disk version of the configuration program, to set the game to run in Direct Draw mode. Rename or move the existing configtool.exe and NlsEng.dll files in the install folder, and extract the disk versions from the zip file. Note that this will also reset the game resolution to what the disk version supported, but you can manually edit the config.div file to change the resolution back.

WineD3D may work better than Direct3D