I too have the infamous black terain and Chesire cat problem. I believe that it is the failure of my video card. I just thought I'd let folks know my setup and hopefully this will prevent another $50 being wasted.

Dell Latitude C640 (Laptop)
1.6ghz Pentium 4
512MB of RAM
Radeon Mobility 7500C w/32mb of RAM and T&L capability and NO shader support.

I am unsure about the current state of my drivers. I will download the updated ones this evening and see if this helps. I have yet to try the reveal map option or done the reveal in the XML file. But like others who have posted in the various threads, I can see the full map normally when I use the map editor. I am now in the market for bare bones desktop barring any incredible stories of folks getting it to work properly on my type of machine. Good luck everybody.

I'll post when I know anything more.

This link to ATI gives the full specs of the card (and the rest of the 7500 serires)

http://www.ati.com/products/comparisons/mobilitycomparison.html

I am one of the unlucky ones with a laptop with integrated Intel graphics, more specifically the 915GM/GMS 910 GML Express Chipset. I fail the hardware requirement test because of the T&L isssue. However, I have preordered Civ4, and will not cancel that because of this. I have not yet read a failure report from someone with a similar chipset (let me know if someone has posted such a message), because I want to test it myself. If you lot are interested, I can notify you about the results of that test, as well as my system requirements as soon as I receive my copy of Civ4.