One thing I like to do when saving games, is use at least two save slots for each and alternate which one I use, just in case something like that happens. You'll still lose some of it, but not everything.
Lol. I alternate over three sometimes four...you just never know eh?
Massive sympathies to you iceonfire...having just recently finished BG2 after quitting out 7 years ago...chapter 5...ouch! I don't know if I could play again in a hurry. How far back was your next save? I think I had about eighty by the time I pwned the jonster.