BTW Did you JUST add the new civ, or did you add/change anything else like governments, civ advances, units, etc?
I did 4 hours worth of tests. I got the original bic file, copied the americans, renamed them "Spain" with adj/noun of Spanish. Saved, and loaded a tiny map with the spanish. Both the spanish and I started on the same small island. I hit F4 (foreign advisor). Everything going good, I saw 3 ? faces. Then I talked to the spanish. We traded techs, then I tried to go back into foreign advisor. Game crashed.
I am sure that this Civilization related as I didn't change anything else. HOWEVER, I still have many tests left.
When you copied, did you tell your new civ to use the animations of the one you copied, or any other existing one? My next test will be to actually make duplicates of all the american-based files, rename them spanish*.*, and try again. Maybe since 2 techs are using the same animations the game gets confused.
I will get back after all my tests. I really want the spanish, but I dont want to overwrite any of the other civs.