Some quick things that fix the problem for some people.
1) Delete the contents of C:\Users\<your name here>\AppData\Local\My Games\Beyond the Sword\cacheFinal thing to try when all else fails
2) Deleting the contents of C\Users\<your name here>\Documents\My Games\Beyond the Sword\CustomAssets.
Note: "Documents" may be "My Documents" on some versions of windows. On my machine it is "Documents\My Documents".
1) Get the program PakBuild.
2) use PakBuild to extract all the art from the FPK files in the Caveman2Cosmos/AssetsClick PAK in the menu area and select Unpack... from the resulting drop down menu3) remove the FPK files from the assets folder.
Select/Go to the Caveman2Cosmos/Assets folder in the folder area. See image 1 attached
Select the the file C2C FPK file
Again select the Caveman2Cosmos/Assets in the new window and press OK.
A fuel gauge will come up and quickly indicate that it has finished. Don't be fooled it takes awhile. Wait for it to disappear. When it does the art that was in the FPK file is now in your art folder.
Do this for each of the FPK files in turn.
4) Your loading of C2C will be much slower but you should not have black tiles any more.
Note. If you were using the alternate terrains you will need to reinstall them after doing this.