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.

It would be better if you post this question in the game subforum (although I am not sure how active it is). The people hanging out there may be better informed or even solved this problem before. It is your best bet.

Okay I'm going to give a try there. Really gutted to not being able to play one of my fav strategy games of all time :(