I've noted that sometimes Civ4 (and Warlords) some of the tile graphics (cities, terrain improvements, numpad help) will turn black, then grey, then back to normal every so often. Is this a graphical bug?

Furthermore, sometimes when I use Command-H to return to the Finder without quitting, and subsequently put the computer to sleep, then the computer restarts for no reason. I've noted that I get the spinning beachball when I try to hide Civ4 and the restart subsequently happens, while on other occasions Civ4 will hide without giving me the beachball, and everything is fine.

How should I avoid this? I've lost quite a bit of work from the computer restarting unexpectedly...

The obvious option is don't let the computer go to sleep. Mine doesn't, as I run Folding@Home continuously, so I can't advise whether your experience is repeatable on my system. Have you reported it to Aspyr Support?

Not yet - it seems like a problem similar to some others that were encountered here. Not to mention that I have still yet to find something repeatable.

It is a 17" MacBook Pro with 3GB RAM, so in theory it should take the highest settings in terms of graphics. I've toned it down to medium and it seems "okay".

I always leave the game using Command-Tab, which since it is in full screen mode hides it anyway. I haven't ever had any problems putting it to sleep at that point. This is also on a MBP. I have gone in and out the game a lot on both of my rigs, with occasionally a problem getting the graphics to display going back into the game, which is usually resolved by using a different method of changing back to the game. But no problems with sleeping with the game running.