I know this might sound as a lazy answer and you guys experiencing this issue have probably already tried doing this, but if you haven't, try any of the following:
- Make sure the game is installed on some folder other than C:\Program Files if you're running any version of Windows Vista upwards (namely 7);
- Try installing and running the game as administrator, and make sure to tinker around with compatibility options -- setting it to Win98 compatibility tends to get the best results, but try and disable desktop composition as well;
- If you have a wireless keyboard or mouse, disconnect and re-connect them again, they tend to be troublesome when it comes to games, especially older ones, like Nox. If you have any wired keyboard and/or mouse, try plugging them in and see if that makes any difference. Make sure to check whether you have the most recent keyboard/mouse drivers;
If, after trying all of this, you still can't solve your problem, I'd reach GOG Support and wait for an answer, or maybe someone more in the know than me can eventually address your particular issue in this thread.
I hope any of this helps you. Happy gaming and, as soon as you get Nox to work, enjoy it, it's a great underrated and overlooked game.