Tech tree screwed up in scenarios?

[seebs]

So, any time I have *ANY* scenario which has "Use default rules" unchecked, the tech tree does the "grey lines, no real connections, can't select techs" thing. If I copy civ3mod.bic into the scenarios directory, open it, and uncheck that menu item, this happens. If I create a "new scenario" and uncheck that menu item, this happens. One person says he's done okay by saving his new scenarios *as* civ3mod.bic, but this seems very disturbing.

Help! Anyone else having this problem? More interestingly, anyone *NOT* having this problem, and if so, are you using LE or Standard?