thanks posila and Killerbee for the the helpful info, a bit of follow-up: - my autosave at the time was set to 20 minutes and at the time i was just clearing biters... so it was no big deal losing 20 minutes out of an 849h game, _autosave1 loaded just fine. - i downloaded Killerbee's re-save and was...

loading up an autosave, game crashed. restarted computer, same thing. no mods

autosave was in taken while I was fighting biters.