Several people have mentioned problems playing larger puzzles, especially after the recent scoring update.
As an experiment, I fired up my old laptop, which started life as Windows XP, and ran puzzle 1505: Aflatoxin Challenge: Round 7. I used only recipes, and kept it going for pretty much the entire two weeks the puzzle was active.
I wasn't using the laptop for anything while 1505 was active.
During this time, I didn't see any crashes or problems until the very end. I restarted the client after every recipe. (After the very last recipe, the client stopped responding, and I had to force it to close. No idea why that happened, there's was nothing in log.txt to explain it, and no debug.txt was generated.)
I ended up with a score of 13,602, good enough for 61st place solo.
To me, this indicates that on Windows 10 at least, Foldit is now relatively stable, and, in theory, even an older system may be able to handle at least one puzzle at a time.
Back when this laptop was on Windows XP, Foldit was not playable. It tended to crash with cryptic Windows error: "The application has requested the runtime to terminate in an unusual way.". My sympathy if you're seeing that.
More details in the next post.