I solved the mystery!
Those green lace socks don't fit because instead of purling the wrong side of the heel flap, I slipped every other stitch. If I'd read the pattern carefully, I probably would have a sock that came out the right size.
That's one pair out of four that didn't work out, so I guess I'm happy enough. My socky enthusiasm has started to fade, but so far nothing more exciting is screaming for me to knit it.
Maybe because I keep starting so darn many quilts. Now it's a 21st Century Bullseye. I did about six blocks last night and can't really decide if it's what I want to do with my big florals or not. I've got to make 48 blocks and then cut each of those into quarters and sew them back other with pieces from the other blocks, and the raw edge applique won't do its thing until the whole thing is quilted and washed, so I won't know until the end if it works. I'm not sure I can handle that much suspense.