I forget how it works exactly, but I think there's a limit on how much XP an individual unit can get from Barbarians. Part of BTS rather than an HR change. I've been meaning to look for a better one for the Explorer. On the todo list. The Druidism founding video sometimes causes crashes, but only on certain graphics cards and not every time. Same with a couple other religion founding videos. I don't know why and I don't know how to fix it. There is a crash in the current beta soon after when Common Market Agreements are signed. Was that what Egypt and Germany signed? There is a 2GB memory limit, but it doesn't cause lag. It causes Memory Allocation Failures (MAFs), either crashing your game or forcing you to exit. After mapsize, unit art is the next biggest contributor to memory usage. In the late game when a lot of the map is revealed and a lot of units are in play, Civ4 is much more likely to hit that 2GB limit. And that's why there aren't any civ-specific variants of late game vehicle units. I'd like to eventually add a little bit of variation though, like maybe 2-5 different varieties of each vehicle where appropriate. Has been fixed. I think it's just a UI bug, but I haven't fixed it yet. Will do so after the Common Market crash (the thing that's still holding release up, sigh).