It hangs up on my other computer as well (which had similar specs {60 gig, all far above recommended, etc} as the laptop, but was a PC instead), but I gave that to my computer to my grandma a few years ago. Yes, it crashes on that one too.
And If i remember correctly, it hangs even on the older computer as well.
could it have something to do with the fact that I included my uber-empire and uber-techs on it? (I modifed the alpa.txt manually, and took a few stuff for myself, such as renaming the singularity laser to plutonic laser and giving it a power of 98, taking 2 shields and making them plutoemp shields, and taking the hunter-seeker algorithim all to myself.)
I also have some factions downloaded from NetworkNode to my SMAC folder and made them replace some of the default factions (IE, i had the Bree replace the hive, since yang's a nuthead and i don't like him).
I don't have alien crossfire, but I hope to get it soon.

(crossfire IS required to play the "return to earth" scenario, right?)
EDIT: Also, can someone PLEASE fix the "box around the cities" problem? I've done everything I can, to no avail. (I have paint shop pro, and networknode.org's tutorial for getting rid of the boxes using PSP simply does NOT work for me)