Cellghast

So the title is self-explanatory. Every time I play an online or skirmish match in Tiberian Sun, the game freezes and I can't click on anything. I can still hear the music in the background and when I alt+tab out and alt+tab back in I get a black screen but can still hear the background music. I want to change the scroll rate in the options but this problem keeps occurring. Please help! I forgot to mention that the options menu works just fine in the full version (beta) for windows. But if I wanted to play on a mac I would still run into this problem.