Most likely its the tech tree - it doesn't have a continuous line from nil to future tech for all the tribes. Since this is stored in the rules.txt, older versions you have will also crash upon loading. The best way to fix this is to manually reverse the last few changes you did to the tech tree via editing the rules.txt.
If that doesn't work, then the next most likely reason is that certain parts of the rules.txt, game.txt or labels.txt were erased accidently. Incrementally replace each file with the default ones (after changing the name of the ones you made) and narrow down the source of the problem.
(additional info: I know you said that earlier versions also crashed but if they didn't crash, then the most likely reason is that the events.txt was edited manually and exceeded the maximum size)
If that doesn't work, then the next most likely reason is that certain parts of the rules.txt, game.txt or labels.txt were erased accidently. Incrementally replace each file with the default ones (after changing the name of the ones you made) and narrow down the source of the problem.
(additional info: I know you said that earlier versions also crashed but if they didn't crash, then the most likely reason is that the events.txt was edited manually and exceeded the maximum size)