Has this issue always been present in your install? If so, then there may be a problem relating to you game or system setup. Try changing resolution, updating graphics drivers and checking that any security software running is not interfering with Divine Divinity (some info on your system specs may help others here).
If the problem has started recently, then try to find out what changed on your system just beforehand. Backing up your savegames (did you start a new game with the GOG version) and reinstalling would be the last resort.
For the record, I've run both the GOG and original versions without encountering the issue you describe.
