Alias for mac is a 64bit application. I think your OS X on your mac is running in legacy mode (32bit mode). I think that might be reason for the problem. Please run Chess application and open Activity Monitor. If it says Intel instead of Intel 64bit, then your OS X is running in 32 bit mode.. I am not sure whether your hardware allows you to run in 64bit mode .. I suppose one would need a Core 2 duo instead of core duo .. hope it helps ..