I realized it was the subform asking me to confirm changes. The subform was an autoform, and I think what I did was change the underlying table slightly, and then the autoform is trying to change it back. Since it is on a back end, it can never do this. So I removed the autoform subform and rebuilt it from scratch and it works fine.
Thanks for pointing me in the right direction, although "bostek" might email you and tell you "look, if you do not have sense answer try not to respond" as he did to me when I posted a similar attempt to point someone in the right direction.