Hey, that worked! The only thing I changed to match what you tried was to make the character set 0123456789abcdef (before, the character set was on the "default"/strong set, the one that comes up first in the pop-up menu). But, I even tried switching it back to that one and it still works - now the password it generates for yahoo is, F@0.`r6#, whether I use the auto-fill or the dialog (yay!).
I don't know why that fixed it, but hopefully it will stay fixed :) Thanks for your help!!