I've just bought and downloaded Stronghold Crusader 2 on my Mac and when I started playing the game for the first time, it was lagging and slow (no idea why) so I changed the resolution of the game from 1024x768 to 800x600 and the performance of the game improved drastically, to which no more lagging of course. However when I quit the game and tried to re-open it, the game couldn't be open although the icon of the game remains opened. How do I fix this? Much help is needed here.